81j

81k

14a

81g

14b

14b

14e

81j

14e

81l

81k

14b

81i

81i

81i

14a

81i

14a

81d

81i

81d

14c

81i

81i

14f

81d

81i

81j

81g

81k

14b

22aa

14b

14b

22x

Santa Cruz Island

San Clemente Island

Santa Miguel Island

San Nicolas Island

Santa Catalina Island

Santa Rosa Island

Santa Barbara Island

Anacapa Island

Farallon Islands

Goose

Lake 

Shasta

Lake

Honey Lake 

Clear

Lake 

Lake

Tahoe

Mono

 Lake

 Lake

Mead 

Salton

Sea

Sacramento River

Owens

Lake 

Isabella

Lake 

Owens River

Mojave River

Colorado

SAN PABLO

BAY

MONTEREY

 BAY

SANTA

MONICA

BAY

SAN

 FRANCISCO

BAY

Lake

Berryessa 

Pyramid

 Lake 

Lake Almanor 

Eagle

Lake 

Clear Lake 

Reservoir

Lower

Klamath

Lake

Tule Lake

Sump

Folsom

Lake

Camanche

Reservoir

Lake

Oroville

Don Pedro

Reservoir

Lake

McClure

San Luis

Reservoir

Millerton

Lake

Pine Flat

Reservoir

Lake

Kaweah

Lake

Success

Lake

Crowley

Walker

Lake

SAN PEDRO

BAY

DRAKES

BAY

Pit River

Pit

River

Klamath River

Klamath

River

Trinity

River

Mad

River

Eel River

Mattole

River

Eel

River

Russian

River

Feather River

Truckee

River

Carson River

Walker River

Amargosa

River

Santa

Margarita

River

San Luis Rey River

San

Diego River

Santa

Ana

River

Big Bear

Lake Lake

Arrowhead

Lake

Cachuma Santa Ynez River

Cuyama River

Santa Maria River

Twitchell

Reservoir

 Lake

Nacimiento

Lake

San Antonio

California

Aqueduct

San

Joaquin

River

Kings

River

Kern River

Merced

River

Merced River

Tuolumne River

Stanislaus

River

San

Joaquin

River

Mokelumne

River

Cosumnes

River

American River

Bear River

Yuba

River

Los Angeles Aqueduct

California Aqueduct

San Gabriel

Rive

L

r

os

Angeles

River

Lake

Henshaw

El Capitan

Lake

Barrett

Lake Morena

Reservoir

Lake Hodges

ESTERO

BAY

SAN LUIS

OBISPO

BAY

Golden Gate

Lake

Havasu

Lake

Mohave

Colo

rado

River

PA

C I F I C

O C E A N

San Felipe

Creek

Alamo

River

New River

River

Aqueduct

Colorado

Chemehuevi Wash

Danby

 Lake

Bristol

Lake

Rogers

Lake

Searles

Lake

Salmon

River

Creek

Cache

Redwood Creek

Noyo River

Big River

Navarro River

Suisun Bay

Estrella

River

Salinas

River

San

Benito

River

Shasta

River

Tule River

Fresno

Slough

Sisquoc River

Lake

 Casitas

Castaic

Lake

Santa

Clara

River

Sespe Creek

Carrizo

Wash

SANTA BARBARA CHANNEL

R

iver

Soda

 Lake

Cadiz 

Lake

Rosamond

Lake

El Mirage Lake

Harper Lake

Lucerne

Lake

Koehn

Lake 

Ivanpah

Lake

Lake

 Davis

Clair

Engle

Lake

Ford Dry Lake

Palen Lake

Dale Lake

Troy

Lake

 Coyote

Lake

 China

Lake

Mesquite Lake

DEATH

VALLE

Y

IMPERIAL

VALLE

Y

Point Conception

Point Arquello

Point Loma

Point Sur

Point Reyes

Bodega Head

Point Arena

Trinidad Head

Point St. George

S A N J O A Q U I N

VA L L E Y

S A C R A M E N T O

VA L L E Y

AMARGOSA

DESERT

ANTELOPE VALLEY

Dana Point

Point Dume

Point Lobos

WHITE

MO

UNTAINS

PANA M INT

RAN G E

PANAMINT

VALLE

Y

COACHELLA

VALLEY

CHUCKWALLA

VALLEY

WARD

VA

L

L

E

Y

LANFAIR

VALLEY

EUREKA

VALLEY

A

R

G

US

RA

NGE

COSO

RANGE

SAN

JACINTO

MTS

SAN BERNARDINO MOUNTAINS

SAN GABRIEL MOUNTAINS

S A N TA Y N E Z M O U N TA I N S

SAN RAFAEL MOUNTAINS

SIERRA MADRE MOUNTAINS

T E H A C H A P I

M O U N TA I N S

S

A

N

T A

L

U C I A

R A N G E

D I A

B

L

O

R A N G E

SANTA

CRUZ

MOUNTAINS

KING

RANGE

SANTA MONICA MOUNTAINS

LITTLE SAN BERNARDINO MOUNTAIN

S

S

ANTA

ANA

MOUNTAINS

WA

RNER

M

O

UN

TAINS

GABILAN

RANGE

CALIENTE

RANGE

S

I

E

R

R

A

N

E

V

A

D

A

C

A

S

C

A

D

E

R

A

N

G

E

K

L

A

M

A

T

H

M

O

U

N

T

A

I

N

S

C

O

A

S

T

R

A

N

G

E

S

C

O

A

S

T

R

A

N

G

E

S

VA

CA

MTS

BLUE

RIDGE

M AYA C M A S

M O U N TA I N S

C A R R I Z O

P L A I N

SURPRISE

VALLEY

MADELINE PLAINS

CHOCOLATE

MOUNTAINS

CHUCKWALLA

MOUNTAINS

EAGLE MOUNTAINS

PALEN

MTS

W HIPPLE MTS

BRISTOL

MOUNTAINS

BULLION MOUNTAINS

IVANPAH

VALLEY

KINGSTON RANGE

SPRING

MOUNTAINS

SILURIAN

VALLEY

B

L

A

C K

M O U N T A I N S

F U N E R A L

M O U N TA I N S

SALINE

VALLEY

BIG VALLEY

FALL RIVER

VALLEY

S H A S TA VALLEY

SIERRA

VALLEY

COTTONWOOD MOUNTAINS

.

.

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.

.

.

.

.

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.

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.

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.

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Z

Z

.

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.

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.

.

Anaheim

San Diego

Santa Ana

Long

Beach

Alturas

Riverside

Los Angeles

Las Vegas

Fresno

San Jose

San

Francisco

Oakland

Sacramento

Carson

City

Redding

Eureka

Crescent

City

Susanville

Red Bluff

Chico

Ukiah

Santa

Rosa

Napa

Fairfield

Vallejo

Concord Stockton

Hayward Modesto

Santa Cruz

Salinas

San Luis

Obispo

Santa

Maria

Bakersfield

Visalia

Lancaster

Santa

Barbara

Oxnard Pasadena San 

Bernardino

Victorville

Merced

Tijuana

El Centro

Mexicali

Yuma

Reno

Oceanside

Monterey

Fallon

Hawthorne

Bridgeport

Tonopah

Goldfield

Beatty

Pahrump

Henderson

Laughlin

Yreka

Weed

Mount Shasta

Dunsmuir

Yuba

City

Paradise

Quincy

Grass Valley

Calexico

Brawley

Arcata

Ventura

Camarillo

Santa Paula

Thousand

Oaks

Burbank

Santa

Clarita

Ontario

Palmdale

Huntington Beach

Escondido

Temecula

Indio

Palm Springs

Barstow

El Cajon

Chula

Vista

Encinitas

Bishop

Davis

Placerville

Auburn

Lodi

South Lake Tahoe

Santa

Clara

Berkeley

Fremont

Livermore

Los Banos

Tracy

Lompoc

Paso

Robles

Fort

Bragg

Needles

Blythe

San

Rafael

Baker

Ramona

NEVADA

NEVADA

OREGON

IDAHO

UTAH

ARIZONA

BAJA CALIFORNIA

MEXICO

Yosemite

National Park

#

Lassen Volcanic

National Park

#

Redwood

National Park

#

Kings Canyon

National Park

#

Sequoia #National Park

Death Valley

National Park#

Joshua Tree

National Park

#

Mojave

National

Preserve

#

78a

9g

9g

9h

9h

9i

9j

9j

5c

5c

13x

13aa

78g 9t

78h

78h 78e

78a

4f

1i

78d 9g

9m

13h

80g

80d

13x

13y

13x

14h

14b

14c

14f

13u

14g

14b

14b

14b

14b

14e

13y

13v

13v

13w

81g

5b

13y

13h

13y

13y

13ac

13y

1h 78b 78b

78f

78f

78b

13j

80d

80e

80j

80j

80j

80d

80j

80d

80e

80a

80a

80a

80b

80a

80a

13c

13r 13s

13s

13s

13y

13x

13w

13w

13w

13w

13w

13s

13v

13w

13w

14f

14a

14c

14d

14c

14e

14d

14b

14a

22d

14a

14a

14a

14c

80d

80j

80j

80j

80j

80j

80l

80j

13x

13x

13j

13x

13v

13v

13h 13h

13t

13t

13r

13t 13h

13t

13t

13t

13t

13r

13s

14b

14b

14b

14b

14f

14b

14b

14f

14c

14b 14b

14f

14b 14f

14b

14b

14b

14b

14b

14b

14b

14f

14b

14b

14b 14b

14b

14b

14b

14b

14c

14f

14b

14b

13h

13h

13h

13h

13w 13h

13h

13v 13v

13h

13v

13s

13s

13h

13v

13w

13v

13h

13w

13v

80h

80c

1a

13y

13y

13aa

14e

14b

1a

1a

9g

9h

9i

9j

1l

1k

6m

6l

6g

6h

7a

7b

7g

7a

7b

7c

1m

1k

6o

6s

6t

6r

6p

1n 6x

1o

6q

1m

8a

6ap

6aq

85a

6aq

6ai

85i

6i

6j

6k

6g

6l 6k

6g

6k

6q 7j

6n

6p

7h

7h

7c

7a

7l

7k

6d

6b

5h

5c

5g

5b

5a

5c

5f

6a

4h

7a

7f

5e

5c

5c

5d

5b

5b

5c 5f

13ab

13aa

9t 78g

78h

78e

6w

6v

6y

6af

6ah

6ag

6al

6r

6z

6aa

6aa

6aa

6ab

7q

7o

7m

7p

7d

6aj

6u

7n

6c

6am

6ao

6ak

6an

6ac

6ab

1i

78d

1j

9g

9m

78q

78r

6f

6e

7a

7e

13h

80g

80j

80j

80j

80d

9p

5c

5c 5c

5c

9q

9r

9l

4g

4f

4f

4f

4f

4f

4e

4f

4e

4e

4e

4e

4d

78k

80d

9n

9o

9l

9l

9l 4f

4f

78l

4e

4e

4g

9g

9s

78l

4d

4e

4e

4g

9k

78l

78n

78o

78p

78a

78k

78k

78o

78m

78o

78l 78l

78d

78o

78i

78o

78o

78d

78k

78k

78d 78j

78d

78j

78i

78d

78i

78l

78l

78l

78l

78l

78j

78d 78d

5c

5c

13x

13x

14f

5j

14l

14k

14f

14j

14l

14l

14l

14f

14l 14j

14l

14m

14l

14h

14i

14b

14c

14b

14l

13u

14b

14f

14g

14b

14f

14b

14b

14n

14b

14b

14c

14b

14c

14b

14a

14b 14b

14b 14e

14b

14b

14c

14c

14c

14o

14b 14f

14a

14b

14o 14b

14b

14b

14j

14b

14k

14j

14j

14f

14k

14k

14f

14k

14k

14f

14k

14k

14f 14f 14k

14k

14k

14n

14f

14k

14k

8e

8c

8f

85d

85c

85c

85l

85k

8d

8d

14f

14k

14f

85l

85l

8d

8f 8d

14k 14k

14k 14f

81e

14b

14b

14k

14k

14f

14n

14n

14f

14n

14a

14b

14b 14b

14b

14f

14b

14b

14b

14f 14b

14b

14j

14b

14a

14b

14a

14b

14f

14b

85c

85j

85j

85j

85i

14k

14f

6ad

14k

8f

8f

8f

8f

8f

85c

85c

85c

8f

85b

8b

8b

13x

13y

13y

13v

14j

14f

14a 14b

14f

14b

13u

14j

81g

81j

81i

81i

81d

81j

81f 81c

81a

81a

81a

81b

81b

85h

8f

8e

8f

85g

85f

85e

81j

81i

81i

81i 81d

81i

81i 81d

81i

81i

81i

14b

81i

81i

81i

14b

81i

14b

14b

14o 14f

14o

14f 14o

14a

14n

14b

14f

14f

14n

14b

14c

14c

14o

81b

81a

8f

8f

8f

8f

8f

8f

8d

85k

85l

85l

85l

85l

85m

13y

13ad

13aa

13y

5b

5a

5k

5i

5a

5a

5a

5a

5a

5m

5n

5a

5a

5a 5a

5a

5k

5l 5a

13aa

13ac

13ae

13ad

13y

13v

13y

5l

5o

5n

5m 5i 5m

5l

5l

6ae

7s

7s

7t

7v

7r

7v

7u

5a

5k

5k

7d

7d

7d

7d

14b

14k

14k

14k

14k

14k

81h

78i

78j

13aa

6l

6h

6f

6t

6aa

6z

6ai

6ap 8a

85c

8g

8c

8e

14j

8e

85k

81g

81j

81j

14h

5j

5n

5i

5k

5l

5l

5i

6k

5c

5c

78d

78m

14a

6b

7a

5f

5f

7e

6ab

6ar

14a

81h

81h

14o

14o

14o

14o

85i

78i

78e

85e

81a

81g

14a

14a

5m

5m

5n

5k

5d

4f

4f

14h

85f

6r

7d

81k

14b

14a

14k

1m

85j

5m

5l

13x

9p

14b

114°

115°

115°

116°

116°

117°

117°

118°

118°

119°

119°

120°

120°

121°

121°

122°

122°

123°

123°

124°

124°

42°

42°

41°

41°

40°

40°

39°

39°

38°

38°

37°

37°

36°

36°

35°

35°

34°

34°

33°

33°

1 Coast Range

1a Coastal Lowlands 

1i Northern Franciscan Redwood Forest

1j King Range/Mattole Basin

1k Coastal Franciscan Redwood Forest

1l Fort Bragg/Fort Ross Terraces

1m Point Reyes/Farallon Islands

1n Santa Cruz Mountains

1o San Mateo Coastal Hills 

4 Cascades

4d Cascade Subalpine/Alpine 

4e High Southern Cascades Montane Forest 

4f Low Southern Cascades Mixed Conifer Forest

4g California Cascades Eastside Conifer Forest

4h Southern Cascades Foothills

5 Sierra Nevada

5a Sierran Alpine

5b Northern Sierra Subalpine Forests

5c Northern Sierra Upper Montane Forests

5d Northern Sierra Mid-Montane Forests

5e Northern Sierra Lower Montane Forests

5f Northeastern Sierra Mixed Conifer-Pine Forests

5g Central Sierra Mid-Montane Forests

5h Central Sierra Lower Montane Forests

5i Eastern Sierra Great Basin Slopes

5j Eastern Sierra Mojavean Slopes

5k Southern Sierra Subalpine Forests

5l Southern Sierra Upper Montane Forests

5m Southern Sierra Mid-Montane Forests

5n Southern Sierra Lower Montane Forest and Woodland

5o Tehachapi Mountains

6 Central California Foothills and Coastal Mountains

6a Tuscan Flows 

6b Northern Sierran Foothills

6c Southern Sierran Foothills

6d Camanche Terraces

6e Tehama Terraces

6f Foothill Ridges and Valleys 

6g North Coast Range Eastern Slopes 

6h Western Valley Foothills/Dunnigan Hills 

6i Clear Lake Hills and Valleys

6j Mayacmas Mountains

6k Napa-Sonoma-Lake Volcanic Highlands 

6l Napa-Sonoma-Russian River Valleys

6m Sonoma-Mendocino Mixed Forest

6n Bodega Coastal Hills

6o Marin Hills

6p Bay Flats

6q Suisun Terraces and Low Hills

6r East Bay Hills/Western Diablo Range

6s San Francisco Peninsula

6t Bay Terraces/Lower Santa Clara Valley

6u Livermore Hills and Valleys 

6v Upper Santa Clara Valley

6w Monterey Bay Plains and Terraces

6x Leeward Hills 

6y Gabilan Range

6z Diablo Range

6aa Eastern Hills

6ab Pleasant Valley/Kettleman Plain

6ac Temblor Range/Elk Hills

6ad Grapevine Transition 

6ae Tehachapi Foothills

6af Salinas Valley

6ag Northern Santa Lucia Range 

6ah Santa Lucia Coastal Forest and Woodland

6ai Interior Santa Lucia Range

6aj Southern Santa Lucia Range

6ak Paso Robles Hills and Valleys

6al Salinas-Cholame Hills

6am Cuyama Valley

6an Carrizo Plain 

6ao Caliente Range

6ap Solomon-Purisima-Santa Ynez Hills

6aq Santa Maria/Santa Ynez Valleys 

6ar Upper Sacramento River Alluvium

13 Central Basin and Range

13h Lahontan and Tonapah Playas

13u Tonopah Basin

13v Tonopah Sagebrush Foothills

13x Sierra Nevada-Influenced Ranges

13y Sierra Nevada-Influenced High Elevation Mountains

13aa Sierra Nevada-Influenced Semiarid Hills and Basins

13ab Sierra Valley

13ac Upper Owens Valley

13ad Mono-Adobe Valleys

13ae Bishop Volcanic Tableland

14 Mojave Basin and Range

14a Eastern Mojave Basins 

14b Eastern Mojave Low Ranges and Arid Footslopes 

14c Eastern Mojave Mountain Woodland and Shrubland 

14e Arid Valleys and Canyonlands 

14f Mojave Playas 

14g Amargosa Desert 

14h Death Valley/Mojave Central Trough

14i Mesquite Flat/Badwater Basin

14j Western Mojave Basins

14k Western Mojave Low Ranges and Arid Footslopes

14l Western Mojave Mountain Woodland and Shrubland

14m Western Mojave High Elevation Mountains

14n Mojave Lava Fields

14o Mojave Sand Dunes

78 Klamath Mountains/California High North Coast Range

78a Rogue/Illinois/Scott Valleys 

78d Serpentine Siskiyous 

78e Inland Siskiyous 

78g Klamath River Ridges 

78h Border High-Siskiyous

78i Western Klamath Low Elevation Forests

78j Western Klamath Montane Forests

78k Eastern Klamath Low Elevation Forests

78l Eastern Klamath Montane Forests

78m Marble/Salmon Mountains-Trinity Alps

78n Scott Mountains

78o Klamath Subalpine

78p Duzel Rock

78q Outer North Coast Ranges

78r High North Coast Ranges

80 Northern Basin and Range

80d Pluvial Lake Basins

80g High Lava Plains

80j Semiarid Uplands 

9 Eastern Cascades Slopes and Foothills

9g Klamath/Goose Lake Basins 

9h Fremont Pine/Fir Forest 

9i Southern Cascades Slope 

9j Klamath Juniper Woodland/Devils Garden 

9k Shasta Valley

9l Pit River Valleys 

9m Warner Mountains 

9n High Elevation Warner Mountains

9o Likely Tableland

9p Modoc/Lassen Juniper-Shrub Hills and Mountains

9q Adin/Horsehead Mountains Forest and Woodland

9r Adin/Dixie Low Hills

9s Modoc Lava Flows and Buttes

9t Old Cascades 

81 Sonoran Basin and Range

81a Western Sonoran Mountains

81b Western Sonoran Mountain Woodland and Shrubland

81c Western Sonoran Basins

81d Sand Hills/Sand Dunes

81e Upper Coachella Valley and Hills

81f Imperial/Lower Coachella Valleys

81g Lower Colorado/Gila River Valleys

81h Sonoran Playas

81i Central Sonoran/Colorado Desert Mountains

81j Central Sonoran/Colorado Desert Basins

81k Arizona Upland/Eastern Sonoran Mountains

85 Southern California/Northern Baja Coast

85a Santa Barbara Coastal Plain and Terraces

85b Oxnard Plain and Valleys

85c Venturan-Angeleno Coastal Hills

85d Los Angeles Plain

85e Diegan Coastal Terraces 

85f Diegan Coastal Hills and Valleys

85g Diegan Western Granitic Foothills

85h Morena/Boundary Mountain Chaparral

85i Northern Channel Islands

85j Southern Channel Islands

85k Inland Valleys

85l Inland Hills

85m Santa Ana Mountains

7 Central California Valley

7a Northern Terraces

7b North Valley Alluvium 

7c Butte Sink/Sutter and Colusa Basins 

7d Southern Hardpan Terraces

7e Sacramento/Feather Riverine Alluvium

7f Sutter Buttes 

7g Yolo Alluvial Fans

7h Yolo/American Basin

7j Delta

7k Lodi Alluvium

7l Stockton Basin

7m San Joaquin Basin

7n Manteca/Merced Alluvium

7o Westside Alluvial Fans and Terraces

7p Granitic Alluvial Fans and Terraces

7q Panoche and Cantua Fans and Basins

7r Tulare Basin/Fresno Slough

7s Kern Terraces

7t South Valley Alluvium

7u Antelope Plain 

7v Southern Clayey Basins

8 Southern California Mountains

8a Western Transverse Range Lower Montane Shrub and Woodland

8b Western Transverse Range Montane Forest

8c Arid Montane Slopes

8d Southern California Subalpine/Alpine

8e Southern California Lower Montane Shrub and Woodland

8f Southern California Montane Conifer Forest

8g Northern Transverse Range

Level III boundary

Level IV boundary

International boundary

State boundary

County boundary

6

13

43

47

18

5 21

75

42

27

7

24

81

20

22

39

65

14

26

30

72

25

17

54

11

25

10

80

34

4

46

44

9

16

31

29 35

45

50

82

42

56

71

51

40

55

79

60

50

73

1

78

67

15

70

40

77

52 53

3

69

48

28

58

76

58

2

41

4

19

23

17

17

8

38

37

36

85

57

68

67

66

64

63

63

84

74

59

49

62

61

23

83

Map Source: USEPA, 2013

 1 Coast Range

 2 Puget Lowland

 3 Willamette Valley

 4 Cascades

 5 Sierra Nevada

 6 Central California Foothills and

 Coastal Mountains

 7 Central California Valley

 8 Southern California Mountains

9 Eastern Cascades Slopes and Foothills

10 Columbia Plateau

11 Blue Mountains

12 Snake River Plain

13 Central Basin and Range

14 Mojave Basin and Range

15 Northern Rockies

16 Idaho Batholith

17 Middle Rockies

18 Wyoming Basin

19 Wasatch and Uinta Mountains

20 Colorado Plateaus

21 Southern Rockies

22 Arizona/New Mexico Plateau

23 Arizona/New Mexico Mountains

24 Chihuahuan Deserts

25 High Plains

26 Southwestern Tablelands

27 Central Great Plains

28 Flint Hills

29 Central Oklahoma/Texas Plains

30 Edwards Plateau

31 Southern Texas Plains

32 Texas Blackland Prairies

33 East Central Texas Plains

34 Western Gulf Coastal Plain

35 South Central Plains

36 Ouachita Mountains

37 Arkansas Valley

38 Boston Mountains

39 Ozark Highlands

40 Central Irregular Plains

41 Canadian Rockies

42 Northwestern Glaciated Plains

43 Northwestern Great Plains

44 Nebraska Sand Hills

45 Piedmont

46 Northern Glaciated Plains

47 Western Corn Belt Plains

48 Lake Agassiz Plain

49 Northern Minnesota Wetlands

50 Northern Lakes and Forests

51 North Central Hardwood Forests

52 Driftless Area

53 Southeastern Wisconsin Till Plains

54 Central Corn Belt Plains

55 Eastern Corn Belt Plains

56 Southern Michigan/Northern 

 Indiana Drift Plains

57 Huron/Erie Lake Plains

58 Northeastern Highlands

59 Northeastern Coastal Zone

60 Northern Allegheny Plateau 

61 Erie Drift Plain

62 North Central Appalachians

63 Middle Atlantic Coastal Plain

64 Northern Piedmont

65 Southeastern Plains

66 Blue Ridge

67 Ridge and Valley

68 Southwestern Appalachians

69 Central Appalachians

70 Western Allegheny Plateau

71 Interior Plateau

72 Interior River Valleys and Hills

73 Mississippi Alluvial Plain

74 Mississippi Valley Loess Plains

75 Southern Coastal Plain

76 Southern Florida Coastal Plain

77 North Cascades

78 Klamath Mountains/California

 High North Coast Range

79 Madrean Archipelago

80 Northern Basin and Range

81 Sonoran Basin and Range

82 Acadian Plains and Hills

83 Eastern Great Lakes Lowlands

84 Atlantic Coastal Pine Barrens

85 Southern California/Northern

 Baja Coast

Level III Ecoregions of the Conterminous United States

Photo credits (by ecoregion): (1) National Park Service, (4) Lyn Topinka, USGS, (5) Phil Gavenda, (6) Glenn Griffith, USGS, (7) Glenn Griffith, USGS, (8) USDA–Forest Service, (9) USDA–Forest Service, 

(13) Glenn Griffith, USGS, (14) National Park Service, (78) Glenn Griffith, USGS, (80) Mike Benzon, (81) Michael Charters, (85) Bruce Perry, California State University, Long Beach.

1. COAST RANGE

Ecoregion 1 covers the coastal mountains of western Washington, western Oregon, and northwestern 

California. These low mountains are covered by highly productive, rain-drenched evergreen forests. 

Sitka spruce forests originally dominated the fog-shrouded coast, and a mosaic of western redcedar, 

western hemlock, and seral Douglas-fir blanketed inland areas. Today, Douglas-fir plantations are 

prevalent on the intensively logged and managed landscape. In California, redwood forests are a 

dominant component of the region, along with some hardwoods such as tanoak, madrone, bigleaf 

maple, California bay, and red alder. Beach pine and Bishop pine occur in many coastal sites. In 

Oregon and Washington, soils typically are Inceptisols and Andisols, whereas in California, Alfisols 

are common. Isomesic soil temperatures occur along the coast, and mesic soils occur inland in 

Oregon and Washington. Landslides and debris slides are common, and lithology influences 

land-management strategies. Coastal headlands, high and low marine terraces, sand dunes, and 

beaches also characterize the region.

4. CASCADES

This mountainous ecoregion stretches from the central part of western Washington, through the spine 

of Oregon, and includes a disjunct area in northern California. It is underlain by Cenozoic volcanics 

and much of the region has been affected by alpine glaciation. Some peaks are higher than 14,000 

feet. Soils have mostly cryic and frigid temperature regimes, with some mesic soil temperatures at 

low elevations and in the south. Andisols and Inceptisols are common. The Cascades have a moist, 

temperate climate that supports an extensive and highly productive coniferous forest, with large 

areas intensively managed for logging. At low elevations in Oregon and Washington, Douglas-fir, 

western hemlock, western red cedar, big leaf maple, and red alder are typical. At higher elevations, 

Pacific silver fir, mountain hemlock, subalpine fir, noble fir, and lodgepole pine occur. In southern 

Oregon and California, more incense cedar, white fir, and Shasta red fir occur along with other 

Sierran species. Jeffrey and ponderosa pines are at many mid-elevation locations in the California 

Cascades. Subalpine meadows, conifers of whitebark pine and mountain hemlock, and rocky alpine 

zones occur at the highest elevations.

5. SIERRA NEVADA

Ecoregion 5 is a mountainous, deeply dissected, and westerly tilting fault block. The central and 

southern part of the region is largely composed of granitic rocks that are lithologically distinct from 

the mixed geology of Ecoregion 78 to the west and the volcanic rocks of the Cascades ecoregion (4) 

to the north. In the northern Sierra Nevada, however, the lithology has similarities to the Klamath 

Mountains. A high fault scarp divides the Sierra Nevada (5) from the Northern Basin and Range (80) 

and Central Basin and Range (13) ecoregions to the east. Near this eastern fault scarp, the Sierra Nevada

reaches its highest elevations. Here, moraines, cirques, and small lakes are common, being products 

of Pleistocene alpine glaciation. Large areas are above timberline, including the Mount Whitney 

summit in California, the highest point in the conterminous United States at nearly 14,500 feet. The 

Sierra Nevada casts a rain shadow over Ecoregions 13 and 80 to the east. The ecoregion slopes more 

gently toward the Central California Valley (7) to the west. The vegetation grades from mostly 

ponderosa pine and Douglas-fir at low elevations on the western side, to pines and Sierra juniper on 

the eastern side, and to fir and other conifers at higher elevations. Alpine conditions exist at the 

highest elevations. Large areas are publicly owned Federal land, including several national parks.

6. CENTRAL CALIFORNIA FOOTHILLS AND COASTAL MOUNTAINS

The primary distinguishing characteristic of this ecoregion is its Mediterranean climate of hot dry 

summers and cool moist winters, and associated vegetative cover comprising primarily chaparral 

and oak woodlands; grasslands occur in some low elevations and patches of pine are found at high 

elevations. Surrounding the lower and flatter Central California Valley (7), most of the region 

consists of open low mountains or foothills, but there are some areas of irregular plains and some 

narrow valleys. Large areas are ranchland and are grazed by domestic livestock. Relatively little land 

has been cultivated, although some valleys are major agricultural centers such as the Salinas Valley 

or the wine vineyard centers of Napa and Sonoma Valleys. Natural vegetation includes coast live oak 

woodlands, Coulter pine, and unique native stands of Monterey pine in the west, and blue oak, black 

oak, and grey pine woodlands in the east.

7. CENTRAL CALIFORNIA VALLEY

Flat, intensively farmed plains with long, hot, dry summers and mild winters distinguish the Central 

California Valley ecoregion from its neighboring ecoregions that are either hilly or mountainous, 

covered with forest or shrub, and generally non-agricultural. Ecoregion 7 includes the flat valley 

basins of deep sediments adjacent to the Sacramento and San Joaquin Rivers, as well as the fans and 

terraces around the edge of the valley. The two major rivers flow from opposite ends of the Central 

California Valley, entering into the Sacramento–San Joaquin River Delta and San Pablo Bay. The 

region once contained extensive prairies, oak savannas, desert grasslands in the south, riparian 

woodlands, freshwater marshes, and vernal pools. More than one-half of the region is now in 

cropland, about three-fourths of which is irrigated. Environmental concerns in the region include 

salinity due to evaporation of irrigation water, groundwater contamination from heavy use of 

agricultural chemicals, loss of wildlife and flora habitats, and urban sprawl.

9. EASTERN CASCADES SLOPES AND FOOTHILLS

Ecoregion 9 is in the rain shadow of the Cascade Range. It has a more continental climate than 

ecoregions to the west, with greater temperature extremes, less precipitation, and frequent fires. 

Open forests of ponderosa pine, western juniper, and occasionally Jeffrey pine, are abundant at 

middle elevations. Lodgepole pine and western white pine often are present at the highest elevations 

and distinguish this region from the higher elevation ecoregions to the west where mountain 

hemlock and fir forests are common, and from the lower elevation, drier ecoregions to the east 

where xeric shrubs and grasslands are predominant. Historically, creeping ground fires consumed 

accumulated fuel and devastating crown fires were less common in dry forests. Volcanic cones, 

plateaus, and buttes are common in much of the region. A few areas of cropland and pastureland 

occur in the lake basins or larger river valleys, which also provide habitat for migrating waterfowl, 

such as sandhill cranes, ducks, and geese.

13. CENTRAL BASIN AND RANGE

Ecoregion 13 is composed of north-trending, fault-block ranges and intervening, drier basins. In the 

high-elevation mountains, woodland, mountain brush, and scattered open forest are found. Lowelevation basins, slopes, and alluvial fans are either shrub- and grass-covered, shrub-covered, or 

barren. The potential natural vegetation is, in order of decreasing elevation and ruggedness, scattered 

western spruce-fir forest, juniper woodland, Great Basin sagebrush, and saltbush-greasewood. The 

Central Basin and Range ecoregion (13) is internally drained by ephemeral streams and once 

contained ancient Lake Lahontan. Ecoregion 13 generally is warmer and drier than the Northern 

Basin and Range ecoregion (80) and has more shrubland and less grassland than the Snake River 

Plain ecoregion (12). Soils grade upslope from mesic Aridisols to frigid Mollisols. The land 

primarily is used for grazing. Additionally, some cropland is irrigated in valleys near mountain water 

sources. The region is not as hot as the Mojave Basin and Range (14) and Sonoran Basin and Range 

(81) ecoregions, and it has a greater percentage of land that is grazed.

80. NORTHERN BASIN AND RANGE 

The Northern Basin and Range ecoregion (80) consists of dissected lava plains, rocky uplands, 

valleys, alluvial fans, and scattered mountain ranges. Overall, it is cooler and has more available 

moisture than the Central Basin and Range ecoregion (13), and also is higher and cooler than the 

Snake River Plain ecoregion (12) to the northeast in Idaho. Valleys support sagebrush steppe or 

saltbush vegetation. Cool season grasses, such as Idaho fescue and bluebunch wheatgrass, are more 

common than in Ecoregion 13 to the south. Mollisols also are more common than in the hotter and 

drier basins of the Central Basin and Range ecoregion (13) where Aridisols support sagebrush, 

shadscale, and greasewood. Juniper woodlands occur on rugged, stony uplands. Ranges are covered 

by mountain brush, grasses (for example, Idaho fescue), aspen groves, and, at high elevations in 

Nevada, some forests with subalpine fir. Elevational banding of mountain vegetation is not as 

apparent as it is in Ecoregion 13. Most of Ecoregion 80 is used as rangeland. The western part of the 

ecoregion is internally drained; its eastern stream network drains to the Snake River system.

81. SONORAN BASIN AND RANGE

Similar in topography to the Mojave Basin and Range ecoregion (14) to the north, this ecoregion 

contains scattered low mountains and has large tracts of federally owned land, a large portion of 

which is used for military training. However, the Sonoran Basin and Range ecoregion is slightly 

hotter than the Mojave and contains large areas of paloverde-cactus shrub and giant saguaro cactus, 

whereas the potential natural vegetation in the Mojave is largely creosotebush. Other typical 

Sonoran plants include white bursage, ocotillo, brittlebrush, creosotebush, catclaw acacia, cholla, 

desert saltbush, pricklypear, and mesquite. Microphyll woodland trees and shrubs, such as ironwood, 

blue paloverde, smoketree, and desert willow, generally are unique to this desert, occupying desert 

washes with occasional moisture flow. In the region, winter rainfall decreases from west to east, 

whereas summer rainfall decreases from east to west. Aridisols and Entisols are dominant with 

hyperthermic soil temperatures and extremely aridic soil moisture regimes, creating some harsh 

environments for plant growth. 

14. MOJAVE BASIN AND RANGE

Stretching across southeastern California, southern Nevada, southwestern Utah, and northwestern 

Arizona, Ecoregion 14 is composed of broad basins and scattered mountains that generally are 

lower, warmer, and drier than those of the Central Basin and Range ecoregion (13). Its 

creosotebush-dominated shrub community is distinct from the saltbush–greasewood and 

sagebrush–grass communities to the north in the Central Basin and Range (13) and Northern Basin 

and Range (80) ecoregions; it also differs from the palo verde–cactus shrub and saguaro cactus in the 

Sonoran Basin and Range ecoregion (81) to the south. In the Mojave, creosotebush, white bursage, 

Joshua tree and other yuccas, and blackbrush are typical. On alkali flats, saltbush, saltgrass, alkali 

sacaton, and iodinebush are found. In the mountains, sagebrush, juniper, and singleleaf pinyon occur. 

At high elevations, some ponderosa pine, white fir, limber pine, and bristlecone pine can be found. 

The basin soils are mostly Entisols and Aridisols that typically have a thermic temperature regime; 

they are warmer than those of Ecoregion 13. Heavy use of off-road vehicles and motorcycles in 

some areas has made the soils susceptible to wind and water erosion. Most of Ecoregion 14 is 

federally owned and grazing is constrained by the lack of water and forage for livestock.

78. KLAMATH MOUNTAINS/CALIFORNIA HIGH NORTH COAST RANGE

Ecoregion 78 encompasses the highly dissected ridges, foothills, and valleys of the Klamath and 

Siskiyou Mountains. It extends south into California to include the mixed conifer and montane 

hardwood forests that occur on mostly mesic soils in the North Coast Range mountains. The region’s 

mix of granitic, sedimentary, metamorphic, and extrusive rocks contrasts with the predominantly 

younger volcanic rocks of the Cascades ecoregion (4) to the east. It includes ultramafic substrates, 

such as serpentinite and mafic lithologies that directly affect vegetation. Most of the region was 

unglaciated during the Pleistocene epoch, when it likely served as a refuge for northern plant 

species. The region’s diverse flora, a mosaic of both northern Californian and Pacific Northwestern 

conifers and hardwoods, is rich in endemic and relic species. The mild, subhumid climate of 

Ecoregion 78 is characterized by a lengthy summer drought.

85. SOUTHERN CALIFORNIA/NORTHERN BAJA COAST

This ecoregion includes coastal and alluvial plains, marine terraces, and some low hills in the coastal 

area of Southern California, and it extends over 200 miles south into Baja California. Coastal sage 

scrub and chaparral vegetation communities with many endemic species once were widespread 

before overgrazing, clearance for agriculture, and massive urbanization occurred. Coastal sage scrub 

includes chamise, white sage, black sage, California buckwheat, golden yarrow, and coastal cholla. 

Small stands of the unique Torrey pine occur near San Diego and on one of the Channel Islands. The 

chaparral-covered hills include ceanothus, manzanita, scrub oak, and mountain-mahogany. Coast 

live oak, canyon live oak, poison oak, and California black walnut also occur.

8. SOUTHERN CALIFORNIA MOUNTAINS

Like other ecoregions in central and southern California, the Southern California Mountains ecoregion

has a Mediterranean climate of hot dry summers and moist cool winters. Although Mediterranean 

types of vegetation such as chaparral and oak woodlands predominate in this region, elevations are 

considerably higher, summers are slightly cooler, and precipitation is greater than in adjacent 

ecoregions, resulting in denser vegetation and some large areas of coniferous woodlands. In parts of 

the Transverse Range, a slope effect causes distinct ecological differences. The south-facing slope of 

the range receives more precipitation (30–40 inches) than the northern slope (15–20 inches), but 

high evaporation rates on the southern side contribute to a cover of chaparral. On the northern side 

of parts of the ecoregion, low evaporation, low annual temperatures, and slow snowmelt allows for 

a coniferous forest that blends into desert montane habitats as it approaches the Mojave Basin and 

Range ecoregion boundary. Conifer species, such as Jeffrey, Coulter, and ponderosa pines, occur 

along with sugar pine, white fir, bigcone Douglas-fir, and at the highest elevations, some lodgepole 

and limber pine. Severe erosion problems are common where the vegetation cover has been removed

by fire, overgrazing, or land clearing. Large parts of the region are National Forest public land.

INTERIOR—GEOLOGICAL SURVEY, RESTON, VIRGINIA—2016

U.S. Department of the Interior

U.S. Geological Survey Open-File Report 2016-1021 Sheet 1 of 2

PRINCIPAL AUTHORS: Glenn E. Griffith (USGS), James M. Omernik (USGS), 

David W. Smith (NRCS), Terry D. Cook (NRCS–retired), Ed Tallyn (NRCS), Kendra 

Moseley (NRCS), and Colleen B. Johnson (Raytheon/SRA).

COLLABORATORS AND CONTRIBUTORS: John Rogers (NRCS–retired), Sandra

A. Bryce (Dynamac Corporation), James Weigand (Bureau of Land Management), 

Todd Keeler-Wolf (DFW), Thor Thorson (NRCS), Ben Sleeter (USGS), Julie Evens 

(California Native Plant Society), Robert K. Hall (USEPA), Hazel Gordon (USFS), 

James M. Harrington (DFW), Peter Ode (DFW), James Calzia (USGS), Randy 

Southard (University of California–Davis), Toby O’Geen (University of California–Davis),

Dick McCleery (NRCS), Greg Suba (California Native Plant Society), Hugh Safford 

(USFS), Joseph Furnish (USFS), Alan J. Woods (Oregon State University), Tad Larsen 

(Raytheon/SRA), and Thomas R. Loveland (USGS).

REVIEWERS: Earl B. Alexander (Soils and Geoecology) and John A. Hutchinson (USGS)

SUGGESTED CITATION: Griffith, G.E., Omernik, J.M., Smith, D.W., Cook, T.D., 

Tallyn, E., Moseley, K., and Johnson, C.B., 2016, Ecoregions of California (poster): 

U.S. Geological Survey Open-File Report 2016–1021, with map, scale 1:1,100,000, 

http://dx.doi.org/10.3133/ofr20161021.

This project was partially supported by funds from the U.S. Environmental Protection Agency, 

Region IX, Regional Applied Research Effort (RARE) program.

Scale 1:1,100,000

NAD 1983 California Teale Albers projection

Standard parallels 34° N and 40.5° N

30 10 0 30 60 Miles

60 20 0 60 120 Kilometers

20

40

Commission for Environmental Cooperation Working Group, 1997, Ecological regions of North America—Toward a 

common perspective: Montreal, Quebec, Commission for Environmental Cooperation, 71 p. (map revised 2006).

Griffith, G.E., Omernik, J.M., Johnson, C.B., and Turner, D.S., 2014, Ecoregions of Arizona (poster): U.S. 

Geological Survey Open-File Report 2014-1141, with map, scale 1:1,325,000, 

http://dx.doi.org/10.3133/ofr20141141.

McMahon, G., Gregonis, S.M., Waltman, S.W., Omernik, J.M., Thorson, T.D., Freeouf, J.A., Rorick, A.H., and 

Keys, J.E., 2001, Developing a spatial framework of common ecological regions for the conterminous 

United States: Environmental Management, v. 28, no. 3, p. 293–316.

Miles, S.R., and Goudy, C.B., compilers, 1997, Ecological subregions of California: San Francisco, U.S. 

Department of Agriculture–Forest Service, Pacific Southwest Region, R5-EM-TP-005, and 

http://www.r5.fs.fed.us/ecoregions.

Omernik, J.M., 1987, Ecoregions of the conterminous United States (map supplement): Annals of the 

Association of American Geographers, v. 77, no. 1, p. 118-125, scale 1:7,500,000.

Omernik, J.M., 1995, Ecoregions—A spatial framework for environmental management, in Davis, W.S., and 

Simon, T.P., eds., Biological assessment and criteria-tools for water resource planning and decision 

making: Boca Raton, Florida, Lewis Publishers, p. 49–62.

Omernik, J.M., Chapman, S.S., Lillie, R.A., and Dumke, R.T., 2000, Ecoregions of Wisconsin: Transactions 

of the Wisconsin Academy of Sciences, Arts and Letters, v. 88, no. 2000, p. 77–103.

Omernik, J.M. and Griffith, G.E., 2014, Ecoregions of the conterminous United States—Evolution of a 

hierarchical spatial framework: Environmental Management, v. 54, no. 6, p. 1249–1266.

Thorson, T.D., Bryce, S.A., Lammers, D.A., Woods, A.J., Omernik, J.M., Kagan, J., Pater, D.E., and 

Comstock, J.A., 2003, Ecoregions of Oregon (color poster with map, descriptive text, summary tables, and 

photographs): Reston, Virginia, U.S. Geological Survey (map scale 1:1,500,000).

U.S. Department of Agriculture–Natural Resources Conservation Service, 2006, Land resource regions and 

major land resource areas of the United States, the Caribbean, and the Pacific Basin: Washington, D.C., 

U.S. Government Printing Office, Agriculture Handbook 296, 669 p. plus map.

U.S. Department of Agriculture–Soil Conservation Service, 1981, Land resource regions and major land 

resource areas of the United States: Washington, D.C., U.S. Government Printing Office, Agriculture 

Handbook 296, 156 p.

U.S. Environmental Protection Agency, 2013, Level III ecoregions of the continental United States (revision 

of Omernik, 1987): Corvallis, Oregon, U.S. Environmental Protection Agency–National Health and 

Environmental Effects Research Laboratory, Map M-1, various scales.

Wiken, E., 1986, Terrestrial ecozones of Canada: Ottawa, Environment Canada, Ecological Land 

Classification Series no. 19, 26 p.

Ecoregions denote areas of general similarity in ecosystems and in the type, quality, and 

quantity of environmental resources. They are designed to serve as a spatial framework 

for the research, assessment, management, and monitoring of ecosystems and ecosystem 

components. By recognizing the spatial differences in the capacities and potentials of 

ecosystems, ecoregions stratify the environment by its probable response to disturbance 

(Bryce and others, 1999). These general purpose regions are critical for structuring and 

implementing ecosystem management strategies across Federal agencies, State agencies, 

and nongovernment organizations that are responsible for different types of resources in the 

same geographical areas (Omernik and others, 2000).

The approach used to compile this map is based on the premise that ecological regions 

are hierarchical and can be identified through the analysis of the spatial patterns and the 

composition of biotic and abiotic phenomena that affect or reflect differences in 

ecosystem quality and integrity (Wiken, 1986; Omernik, 1987, 1995). These phenomena 

include geology, physiography, vegetation, climate, soils, land use, wildlife, and 

hydrology. The relative importance of each characteristic varies from one ecological 

region to another regardless of the hierarchical level. A Roman numeral hierarchical 

scheme has been adopted for different levels of ecological regions. Level I is the 

coarsest level, dividing North America into 15 ecological regions. Level II divides the 

continent into 50 regions (Commission for Environmental Cooperation Working Group, 

1997, map revised 2006). At level III, the continental United States contains 105 

ecoregions and the conterminous United States has 85 ecoregions (U.S. Environmental 

Protection Agency, 2013). Level IV, depicted here for California, is a further refinement 

of level III ecoregions. Explanations of the methods used to define these ecoregions are 

given in Omernik (1995), Omernik and others (2000), and Omernik and Griffith (2014). 

California has great ecological and biological diversity. The State contains offshore

islands and coastal lowlands, large alluvial valleys, forested mountain ranges, deserts, 

and various aquatic habitats. There are 13 level III ecoregions and 177 level IV 

ecoregions in California and most continue into ecologically similar parts of adjacent 

States of the United States or Mexico (Bryce and others, 2003; Thorson and others, 

2003; Griffith and others, 2014).

The California ecoregion map was compiled at a scale of 1:250,000. It revises and 

subdivides an earlier national ecoregion map that was originally compiled at a smaller scale 

(Omernik, 1987; U.S. Environmental Protection Agency, 2013). This poster is the result 

of a collaborative project primarily between U.S. Environmental Protection Agency 

(USEPA) Region IX, USEPA National Health and Environmental Effects Research 

Laboratory (Corvallis, Oregon), California Department of Fish and Wildlife (DFW), 

U.S. Department of Agriculture (USDA)–Natural Resources Conservation Service 

(NRCS), U.S. Department of the Interior–Geological Survey (USGS), and other State of 

California agencies and universities.

The project is associated with interagency efforts to develop a common framework of 

ecological regions (McMahon and others, 2001). Reaching that objective requires 

recognition of the differences in the conceptual approaches and mapping methodologies 

applied to develop the most common ecoregion-type frameworks, including those 

developed by the USDA–Forest Service (Bailey and others, 1994; Miles and Goudy, 

1997; Cleland and others, 2007), the USEPA (Omernik 1987, 1995), and the NRCS 

(U.S. Department of Agriculture–Soil Conservation Service, 1981; U.S. Department of 

Agriculture–Natural Resources Conservation Service, 2006). As each of these 

frameworks is further refined, their differences are becoming less discernible. Regional 

collaborative projects such as this one in California, where some agreement has been 

reached among multiple resource-management agencies, are a step toward attaining 

consensus and consistency in ecoregion frameworks for the entire nation. 

Literature Cited:

Bailey, R.G., Avers, P.E., King, T., and McNab, W.H., eds., 1994, Ecoregions and subregions of the United States 

(map) (supplementary table of map unit descriptions compiled and edited by McNab, W.H., and Bailey, 

R.G.): Washington, D.C., U.S. Department of Agriculture–Forest Service, scale 1:7,500,000.

Bryce, S.A., Omernik, J.M., and Larsen, D.P., 1999, Ecoregions—A geographic framework to guide risk 

characterization and ecosystem management: Environmental Practice, v. 1, no. 3, p. 141–155.

Bryce, S.A., Woods, A.J., Morefield, J.D., Omernik, J.M., McKay, T.R., Brackley, G.K., Hall, R.K., Higgins, 

D.K., McMorran, D.C., Vargas, K.E., Petersen, E.B., Zamudio, D.C., and Comstock, J.A., 2003, Ecoregions 

of Nevada (color poster with map, descriptive text, summary tables, and photographs): Reston, Virginia, U.S. 

Geological Survey (map scale 1:1,350,000).

Cleland, D.T., Freeouf, J.A., Keys, J.E., Jr., Nowacki, G.J., Carpenter, C., and McNab, W.H., 2007, Ecological 

subregions—Sections and subsections of the conterminous United States: Washington, D.C., U.S. 

Department of Agriculture–Forest Service, General Technical Report WO-76, scale 1:3,500,000.

Ecoregions of California