0 100 200 300 400 Mi

0 200 400 600 Km

Scale 1:7,500,000

Albers Equal Area Projection

101

104

103

102

105

106

106

107

108

104

109

110

111

112

113

113

116

117

118

119

120

115

114

0 100 200 300 400 Mi

0 200 400 600 Km

Scale 1:16,000,000

Albers Equal Area Projection

101. Arctic Coastal Plain

102. Arctic Foothills

103. Brooks Range

104. Interior Forested Lowlands and Uplands

105. Interior Highlands

106. Interior Bottomlands

107. Yukon Flats

108. Ogilvie Mountains

109. Subarctic Coastal Plains

110. Seward Peninsula

111. Ahklun and Kilbuck Mountains

112. Bristol Bay-Nushagak Lowlands

113. Alaska Peninsula Mountains

114. Aleutian Islands (Western portion not shown)

115. Cook Inlet

116. Alaska Range

117. Copper Plateau

118. Wrangell Mountains

119. Pacific Coastal Mountains

120. Coastal Western Hemlock-Sitka Spruce Forests

CANADA

Albany

Annapolis

Atlanta

Augusta

Austin

Baton

Rouge

Bismarck

Boise

Boston

Carson 

City

Charleston

Cheyenne

Columbia

Columbus

Concord

Denver

Des Moines

Dover

Frankfort

Harrisburg

Hartford

Helena

Indianapolis

Jackson

Jefferson

City

Lansing

Lincoln

Little Rock

Madison

Montgomery

Montpelier

Nashville

Oklahoma 

City

Olympia

Phoenix

Pierre

Providence

Raleigh

Richmond

Sacramento

Saint 

Paul

Salem

Salt 

Lake 

City

Santa 

Fe

Springfield

Tallahassee

Topeka

Trenton

Juneau

Akron

Albuquerque

Birmingham

Buffalo

Charlotte

Chicago

Cincinnati

Cleveland

Colorado 

Springs

Corpus 

Christi

Dallas

Detroit

El Paso

Fort 

Worth

Fresno

Houston

Jacksonville

Lexington

Los 

Angeles

Louisville

Memphis

Miami

Milwaukee

Minneapolis

Mobile

New 

Orleans

New York

Newark

Omaha

Philadelphia

Pittsburgh

Portland

Rochester

San

Antonio

San 

Diego

San

Francisco

San 

Jose

Santa 

Ana

Seattle

Shreveport

Tampa

Toledo

Tucson

Tulsa

Wichita

Baltimore

Saint Louis

Mesa

Washington DC

Kansas City

Norfolk

85

85

8

14

6

7

5

4

78

9

1

4

3

10

11

1

2

77

77

15

10

16

12

80

13

81

79

23

23

20

19

18

17

17

17

17

41

17

42

43

17

17

17

21

23

22

23 23

23

23

23

24

25

30

31 34

32

33

32

29

25

26

25

42

46

44

27

28

40

39

38

37

36

35

40

47

52

50

51

49

48

50 51

53

54

57

56

55

72

71

68

73

74

75

65

57

61

62

69

67

66

70

66

75

76

63

65

45

63

63

64

62

84

84

83

60

58

58 58

58

59

82

84

59

69

1

30

59

Level III Ecoregions of the Continental United States

(Revised April 2013)

National Health and Environmental Effects Research Laboratory

U.S. Environmental Protection Agency

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

 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. Cross Timbers

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

The ecoregions shown here have been derived from Omernik (1987) and from refinements of the U.S. EPA ecoregion 

framework made in numerous state-level projects. These projects, conducted in collaboration with the U.S. EPA regional 

offices, state resource management agencies, and with other federal agencies, typically involved refining ecoregions, defining 

subregions, and locating sets of stream reference sites. Designed to serve as a spatial framework for environmental resource 

management, ecoregions denote areas within which ecosystems (and the type, quality, and quantity of environmental 

resources) are generally similar. The ecoregions have been used to develop regional biological criteria and water quality 

standards and to set management goals for nonpoint source pollution, among other applications. 

The approach used to compile this map is based on the premise that ecological regions can be identified through the analysis of 

the patterns and the composition of biotic and abiotic phenomena that affect or reflect differences in ecosystem quality and 

integrity (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 classification scheme has been adopted for different levels of ecological regions. 

Level I is the coarsest level, dividing North America into 15 ecological regions, whereas at Level II the continent is 

subdivided into 50 classes (CEC 1997, 2006). Level III is the hierarchical level shown on this map, with 105 ecoregions in the 

continental U.S. For the conterminous United States, the ecoregions have been further subdivided to 968 Level IV ecoregions. 

Details about the ecoregions or their applications are explained in reports and publications from the state and regional projects 

(e.g., Bryce et al., 1998, 2003; Chapman et al., 2001, 2006; Gallant et al., 1989, 1995; Griffith et al., 2002, 2004, 2009; 

McGrath et al., 2002; Omernik et al., 2000, 2004; Thorson et al., 2003; Wiken et al., 2011; and Woods et al., 1996, 2002, 

2004). For additional information, contact James M. Omernik, USGS, c/o U.S. EPA, 200 SW 35th Street, Corvallis, OR 

97333, phone (541) 754-4458, email omernik.james@epa.gov; or Glenn Griffith, USGS, c/o US EPA, 200 SW 35th Street, 

Corvallis, OR 97333, phone (541) 754-4465, email ggriffith@usgs.gov.

REFERENCES CITED

Bryce, S.A., J.M. Omernik, D.E. Pater, M. Ulmer, J. Schaar, J. Freeouf, R. Johnson, P. Kuck, and S.H. Azevedo. 1998. Ecoregions 

of North Dakota and South Dakota. (map poster). U.S. Geological Survey, Reston, VA. Scale 1:1,500,000.

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

K.E. Vargas, E.B. Petersen, D.C. Zamudio, and J.A. Comstock. 2003. Ecoregions of Nevada. (map poster). U.S. Geological 

Survey, Reston, VA. Scale 1:1,350,000.

Chapman, S.S., G.E. Griffith, J.M. Omernik, A.B. Price, J. Freeouf, and D.L. Schrupp. 2006. Ecoregions of Colorado. (map 

poster). U.S. Geological Survey, Reston, VA. Scale 1:1,200,000.

Chapman, S.S., J.M. Omernik, J.A. Freeouf, D.G. Huggins, J.R. McCauley, C.C. Freeman, G. Steinauer, R.T. Angelo, and R.L. 

Schlepp. 2001. Ecoregions of Nebraska and Kansas (map poster): U.S. Geological Survey, Reston, VA. Scale 1:1,950,000.

Commission for Environmental Cooperation. 1997. Ecological regions of North America: toward a common perspective. 

Commission for Environmental Cooperation, Montreal, Quebec, Canada. 71 p. Map (scale 1:12,500,000).

Commission for Environmental Cooperation. 2006. Ecological regions of North America – Levels I, II, and III: Montreal, Quebec, 

Canada, Commission for Environmental Cooperation, scale 1:10,000,000, http://www.epa.gov/wed/pages/ecoregions/na_eco.htm.

Gallant, A.L., T.R. Whittier, D.P. Larsen, J.M. Omernik, and R.M. Hughes. 1989. Regionalization as a tool for managing 

environmental resources. EPA/600/3-89/060. U.S. Environmental Protection Agency, Environmental Research Laboratory, 

Corvallis, OR. 152 p.

Gallant, A.L., E.F. Binnian, J.M. Omernik, and M.B. Shasby. 1995. Ecoregions of Alaska. U.S. Geological Survey Professional 

Paper 1567. U.S. Government Printing Office, Washington D.C. 73 p.

Griffith, G.E., S.A. Bryce, J.M. Omernik, J.A. Comstock, A.C. Rogers, B. Harrison, S.L. Hatch, and D. Bezanson. 2004. Ecoregions of 

Texas. (map poster). U.S. Geological Survey, Reston, VA. Scale 1:2,500,000.

Griffith, G.E., J.M. Omernik, S.A. Bryce, J. Royte, W.D. Hoar, J.W. Homer, D. Keirstead, K.J. Metzler, and G. Hellyer. 2009. Ecoregions 

of New England (2 sided color poster with map, descriptive text, summary tables, and photographs). U.S. Geological Survey, Reston, 

VA. Scale 1:1,325,000. 

Griffith, G.E., J.M. Omernik, J.A. Comstock, M.P. Shafale, W.H. McNab, D.R. Lenat, J.B. Glover, and V.B. Shelburne. 2002. 

Ecoregions of North Carolina and South Carolina. (map poster). U.S. Geological Survey, Reston, VA. Scale 1:1,500,000.

McGrath, C.L., A.J. Woods, J.M. Omernik, S.A. Bryce, M. Edmondson, J.A. Nesser, J. Shelden, R.C. Crawford, J.A. Comstock, and 

M.D. Plocher. 2002. Ecoregions of Idaho. (map poster). U.S. Geological Survey, Reston, VA. Scale 1:1,350,000.

Omernik, J.M. 1987. Ecoregions of the conterminous United States. Map (scale 1:7,500,000). Annals of the Association of American 

Geographers 77(1):118-125.

Omernik, J.M. 1995. Ecoregions: A spatial framework for environmental management. In: Biological Assessment and Criteria: Tools 

for Water Resource Planning and Decision Making. Davis, W.S. and T.P. Simon (eds.) Lewis Publishers, Boca Raton, FL. Pp. 49-62.

Omernik, J.M. 2004. Perspectives on the nature and definition of ecological regions. Environmental Management 34 (Suppl. 1): S27-S38.

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

Acadamy of Sciences, Arts, and Letters 88:77-103.

Thorson, T.D., S.A. Bryce, D.A. Lammers, A.J. Woods, J.M. Omernik, J. Kagan, D.E. Pater, and J.A. Comstock. 2003. Ecoregions of 

Oregon. (map poster). U.S. Geological Survey, Reston, VA. Scale 1:1,350,000.

Wiken, E., Jiménez Nava, F., and Griffith, G. 2011. North American Terrestrial Ecoregions - Level III. Commission for Environmental 

Cooperation, Montreal, Canada. 149 p., ftp://ftp.epa.gov/wed/ecoregions/pubs/NA_TerrestrialEcoregionsLevel3_Final-2june11_CEC.pdf.

Woods, A.J., T.L. Foti, Chapman, S.S., J.M. Omernik, J. Wise, E.O. Murray, W.L. Prior, J. Pagan, J.A. Comstock, and M. Radford. 

2004. Ecoregions of Arkansas. (map poster). U.S. Geological Survey, Reston, VA. Scale 1:1,000,000.

Woods, A.J., J.M. Omernik, D.D. Brown, and C.W. Kiilsgaard. 1996. Level III and IV ecoregions of Pennsylvania and the Blue 

Ridge Mountains, the Ridge and Valley, and Central Appalachians of Virginia, West Virginia, and Maryland. EPA/600/R-96/077. 

U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Corvallis, OR. 50 p.

Woods, A.J., J.M. Omernik, W.H. Martin, G.J. Pond, W.M. Andrews, S.M. Call, J.A. Comstock, and D.D. Taylor. 2002. Ecoregions 

of Kentucky. (map poster). U.S. Geological Survey, Reston, VA. Scale 1:1,000,000. CITING THIS MAP: U.S. Environmental Protection Agency, 2013, Level III ecoregions of the continental United States: Corvallis, Oregon, U.S. EPA 

– National Health and Environmental Effects Research Laboratory, map scale 1:7,500,000, http://www.epa.gov/wed/pages/ecoregions/level_iii_iv.htm.