# San Luis Obispo County, California

San Luis Obispo County (/sæn ˌluːɪs oʊˈbɪspoʊ/ ), officially the County of San Luis Obispo, is a county on the Central Coast of California. As of the 2020 United States census, the population was 282,424. The county seat is San Luis Obispo.
Junípero Serra founded the Mission San Luis Obispo de Tolosa in 1772, and San Luis Obispo grew around it. The small size of the county's communities, scattered along the beaches, coastal hills, and mountains of the Santa Lucia range, provides a wide variety of coastal and inland hill ecologies to support fishing, agriculture, and tourist activities.
California Polytechnic State University has almost 20,000 students. Tourism, especially for the wineries, is popular. Grapes and other agriculture products are an important part of the economy. San Luis Obispo County is the third largest producer of wine in California, surpassed only by Sonoma and Napa counties. Strawberries are the largest agricultural crop in the county.
The town of San Simeon is located at the foot of the ridge where newspaper publisher William Randolph Hearst built Hearst Castle. Other coastal towns (listed from north to south) include Cambria, Cayucos, Morro Bay, and Los Osos -Baywood Park. These cities and villages are located northwest of the city of San Luis Obispo. To the south are Avila Beach and the Five Cities region. The Five Cities originally were: Arroyo Grande, Grover Beach (then known as Grover City), Oceano, Fair Oaks and Halcyon. Today, the Five Cities region consists of Pismo Beach, Grover Beach, Arroyo Grande, Oceano, and Halcyon (basically the area from Pismo Beach to Oceano). Just south of the Five Cities, San Luis Obispo County borders northern Santa Barbara County. Inland, the cities of Paso Robles, Templeton, and Atascadero lie along the Salinas River, near the Paso Robles wine region. San Luis Obispo lies south of Atascadero and north of the Five Cities region.

## History

The prehistory of San Luis Obispo County is strongly influenced by the Chumash people. There has been significant settlement here at least as early as the Millingstone Horizon thousands of years ago. Important settlements existed in coastal areas such as Morro Bay and Los Osos.
Mission San Luis Obispo de Tolosa was founded on September 1, 1772, in the area that is now the city of San Luis Obispo. The namesake of the mission, city and county is Saint Louis of Toulouse, the young bishop of Toulouse (Obispo and Tolosa in Spanish) in 1297.
San Luis Obispo County was one of the original counties of California, created in 1850 at the time of statehood.
The Salinas River Valley, a region that figures strongly in several John Steinbeck novels, stretches north from San Luis Obispo County.

## Geography

According to the U.S. Census Bureau, the county has a total area of 3,616 square miles (9,370 km$^2$), of which 3,299 square miles (8,540 km$^2$) is land and 317 square miles (820 km$^2$) (comprising 8.8%) is water.

### Climate

San Luis Obispo County has three main climate types. BSk climate can mainly be found in the eastern portions of the county, along with certain smaller areas in the north. Csa climate can mainly be found in the central portions of the counties, in communities such as Paso Robles. The rest of the county is made up of the Csb climate type. The Csb warm-summer mediterranean type climate together with the county's varied landscapes reminds visitors of European locales.

### National protected areas

* Carrizo Plain National Monument (part)
* Guadalupe-Nipomo Dunes National Wildlife Refuge (part)
* Los Padres National Forest (part)

### Marine Protected Areas

* Cambria State Marine Conservation Area
* Chumash Heritage National Marine Sanctuary
* Morro Bay State Marine Recreational Management Area and Morro Bay State Marine Reserve
* Piedras Blancas State Marine Reserve and Marine Conservation Area
* Point Buchon State Marine Reserve and Marine Conservation Area
* White Rock (Cambria) State Marine Conservation Area

## Demographics
### 2020 census

San Luis Obispo County, California – Racial and ethnic composition Note: the US Census treats Hispanic/Latino as an ethnic category. This table excludes Latinos from the racial categories and assigns them to a separate category. Hispanics/Latinos may be of any race. :
| Race / Ethnicity (NH = Non-Hispanic) | Pop 1990 | Pop 2000 | Pop 2010 | Pop 2020 | % 1990 | % 2000 | % 2010 | % 2020 |
| White alone (NH) | 176,246 | 187,840 | 191,696 | 183,468 | 81.16% | 76.15% | 71.09% | 64.96% |
| Black or African American alone (NH) | 4,325 | 4,743 | 5,128 | 4,330 | 1.99% | 1.92% | 1.90% | 1.53% |
| Native American or Alaska Native alone (NH) | 1,652 | 1,490 | 1,367 | 1,136 | 0.76% | 0.60% | 0.51% | 0.40% |
| Asian alone (NH) | 5,774 | 6,342 | 8,106 | 10,001 | 2.66% | 2.57% | 3.01% | 3.54% |
| Pacific Islander alone (NH) | N/A | 227 | 346 | 340 | N/A | 0.09% | 0.13% | 0.12% |
| Other Race alone (NH) | 242 | 365 | 784 | 1,614 | 0.11% | 0.15% | 0.29% | 0.57% |
| Mixed Race or Multi-Racial (NH) | N/A | 5,478 | 6,237 | 13,614 | N/A | 2.22% | 2.31% | 4.82% |
| Hispanic or Latino (any race) | 28,923 | 40,196 | 55,973 | 67,921 | 13.32% | 16.29% | 20.76% | 24.05% |
| Total | 217,162 | 246,681 | 269,637 | 282,424 | 100.00% | 100.00% | 100.00% | 100.00% |

### 2011

Population, race, and income :
| Total population | 267,871 | 267,871 |
| White | 224,800 | 83.9% |
| Black or African American | 5,882 | 2.2% |
| American Indian or Alaska Native | 2,625 | 1.0% |
| Asian | 8,693 | 3.2% |
| Native Hawaiian or other Pacific Islander | 280 | 0.1% |
| Some other race | 16,666 | 6.2% |
| Two or more races | 8,925 | 3.3% |
| Hispanic or Latino (of any race) | 54,537 | 20.4% |
| Per capita income | $30,204 | $30,204 |
| Median household income | $58,630 | $58,630 |
| Median family income | $74,841 | $74,841 |

#### Places by population, race, and income

Places by population and race :
| Place | Type | Population | White | Other | Asian | Black or African American | Native American | Hispanic or Latino (of any race) |
| Arroyo Grande | City | 17,132 | 85.8% | 6.7% | 5.0% | 1.6% | 0.8% | 12.7% |
| Atascadero | City | 28,194 | 88.5% | 5.7% | 1.7% | 1.7% | 2.4% | 13.7% |
| Avila Beach | CDP | 1,086 | 91.4% | 8.6% | 0.0% | 0.0% | 0.0% | 2.2% |
| Blacklake | CDP | 1,014 | 97.1% | 0.0% | 1.5% | 0.0% | 1.4% | 0.8% |
| Callender | CDP | 1,531 | 96.3% | 2.2% | 1.6% | 0.0% | 0.0% | 42.5% |
| Cambria | CDP | 6,229 | 91.7% | 4.3% | 2.7% | 0.0% | 1.3% | 17.1% |
| Cayucos | CDP | 2,822 | 97.5% | 1.8% | 0.5% | 0.0% | 0.2% | 6.0% |
| Creston | CDP | 94 | 79.8% | 20.2% | 0.0% | 0.0% | 0.0% | 0.0% |
| Edna | CDP | 80 | 100.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% |
| El Paso de Robles (Paso Robles) | City | 29,270 | 76.6% | 15.1% | 2.0% | 4.5% | 1.8% | 35.1% |
| Garden Farms | CDP | 335 | 100.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% |
| Grover Beach | City | 13,175 | 81.6% | 9.9% | 6.0% | 1.4% | 1.0% | 21.0% |
| Lake Nacimiento | CDP | 2,397 | 96.0% | 4.0% | 0.0% | 0.0% | 0.0% | 12.3% |
| Los Berros | CDP | 920 | 86.2% | 13.8% | 0.0% | 0.0% | 0.0% | 19.8% |
| Los Osos | CDP | 14,950 | 85.3% | 7.5% | 6.3% | 0.4% | 0.5% | 12.4% |
| Los Ranchos | CDP | 1,578 | 91.4% | 3.1% | 1.5% | 0.8% | 3.2% | 2.1% |
| Morro Bay | City | 10,263 | 96.0% | 1.7% | 1.8% | 0.1% | 0.4% | 17.8% |
| Nipomo | CDP | 16,622 | 84.1% | 12.7% | 1.3% | 1.3% | 0.6% | 35.0% |
| Oak Shores | CDP | 187 | 100.0% | 0.0% | 0.0% | 0.0% | 0.0% | 5.3% |
| Oceano | CDP | 7,456 | 77.3% | 19.4% | 1.5% | 0.0% | 1.8% | 47.6% |
| Pismo Beach | City | 7,753 | 87.6% | 7.7% | 2.8% | 0.6% | 1.3% | 10.3% |
| San Luis Obispo | City | 45,130 | 83.2% | 8.4% | 6.4% | 1.6% | 0.6% | 16.6% |
| San Miguel | CDP | 2,782 | 64.6% | 29.6% | 1.3% | 0.0% | 4.6% | 50.8% |
| San Simeon | CDP | 571 | 48.0% | 52.0% | 0.0% | 0.0% | 0.0% | 72.5% |
| Santa Margarita | CDP | 1,429 | 95.7% | 4.3% | 0.0% | 0.0% | 0.0% | 18.0% |
| Shandon | CDP | 1,150 | 82.3% | 6.9% | 0.0% | 10.6% | 0.3% | 46.1% |
| Templeton | CDP | 7,645 | 88.9% | 9.5% | 0.7% | 0.5% | 0.4% | 16.4% |
| Whitley Gardens | CDP | 244 | 58.6% | 33.6% | 0.0% | 7.8% | 0.0% | 41.4% |
| Woodlands | CDP | 417 | 89.2% | 3.6% | 3.8% | 0.0% | 3.4% | 11.8% |
Places by population and income :
| Place | Type | Population | Per capita income | Median household income | Median family income |
| Arroyo Grande | City | 17,132 | $34,489 | $64,900 | $79,188 |
| Atascadero | City | 28,194 | $32,153 | $68,502 | $79,818 |
| Avila Beach | CDP | 1,086 | $45,863 | $65,483 | $42,107 |
| Blacklake | CDP | 1,014 | $43,698 | $81,417 | $105,152 |
| Callender | CDP | 1,531 | $25,222 | $72,917 | $91,852 |
| Cambria | CDP | 6,229 | $46,892 | $76,271 | $99,550 |
| Cayucos | CDP | 2,822 | $38,525 | $59,130 | $69,861 |
| Creston | CDP | 94 | $43,934 | $85,357 | $81,250 |
| Edna | CDP | 80 | $71,853 | $115,962 | $115,962 |
| El Paso de Robles (Paso Robles) | City | 29,270 | $26,547 | $57,927 | $63,864 |
| Garden Farms | CDP | 335 | $61,822 | $111,360 | $111,360 |
| Grover Beach | City | 13,175 | $25,232 | $47,708 | $63,354 |
| Lake Nacimiento | CDP | 2,397 | $31,410 | $58,542 | $62,760 |
| Los Berros | CDP | 920 | $15,603 | $36,096 | $36,776 |
| Los Osos | CDP | 14,950 | $30,967 | $57,500 | $73,027 |
| Los Ranchos | CDP | 1,578 | $59,646 | $99,028 | $104,455 |
| Morro Bay | City | 10,263 | $33,137 | $52,582 | $65,833 |
| Nipomo | CDP | 16,622 | $26,014 | $61,265 | $68,386 |
| Oak Shores | CDP | 187 | $44,498 | $97,639 | $98,542 |
| Oceano | CDP | 7,456 | $18,363 | $37,219 | $40,489 |
| Pismo Beach | City | 7,753 | $44,250 | $65,682 | $88,971 |
| San Luis Obispo | City | 45,130 | $25,775 | $42,528 | $80,560 |
| San Miguel | CDP | 2,782 | $17,371 | $49,097 | $42,296 |
| San Simeon | CDP | 571 | $20,490 | $44,583 | $51,786 |
| Santa Margarita | CDP | 1,429 | $19,328 | $49,032 | $58,672 |
| Shandon | CDP | 1,150 | $19,050 | $65,260 | $59,167 |
| Templeton | CDP | 7,645 | $35,743 | $70,820 | $92,169 |
| Whitley Gardens | CDP | 244 | $21,938 | $106,250 | $129,000 |
| Woodlands | CDP | 417 | $54,163 | $96,250 | $89,250 |

### 2010

The 2010 United States census reported that San Luis Obispo County had a population of 269,637. The racial makeup of San Luis Obispo County was 222,756 (82.6%) White, 5,550 (2.1%) African American, 2,536 (0.9%) Native American, 8,507 (3.2%) Asian (1.0% Filipino, 0.6% Chinese, 0.4% Japanese, 0.3% Indian, 0.3% Korean, 0.2% Vietnamese), 389 (0.1%) Pacific Islander, 19,786 (7.3%) from other races, and 10,113 (3.8%) from two or more races. Hispanic or Latino of any race were 55,973 persons (20.8%); 17.7% of San Luis Obispo County is Mexican, 0.3% Puerto Rican, and 0.2% Salvadoran.
Population reported at 2010 United States census :
| The County | Total Population | White | African American | Native American | Asian | Pacific Islander | other races | two or more races | Hispanic or Latino (of any race) |
| San Luis Obispo County | 269,637 | 222,756 | 5,550 | 2,536 | 8,507 | 389 | 19,786 | 10,113 | 55,973 |
| Incorporated cities | Total Population | White | African American | Native American | Asian | Pacific Islander | other races | two or more races | Hispanic or Latino (of any race) |
| Arroyo Grande | 17,252 | 14,710 | 156 | 125 | 595 | 14 | 856 | 796 | 2,707 |
| Atascadero | 28,310 | 24,457 | 585 | 295 | 685 | 57 | 1,205 | 1,026 | 4,429 |
| Grover Beach | 13,156 | 9,964 | 146 | 186 | 542 | 35 | 1,582 | 701 | 3,840 |
| Morro Bay | 10,234 | 8,909 | 44 | 92 | 258 | 9 | 613 | 309 | 1,526 |
| Paso Robles | 29,793 | 23,158 | 622 | 297 | 593 | 56 | 3,916 | 1,151 | 10,275 |
| Pismo Beach | 7,655 | 6,976 | 50 | 41 | 203 | 11 | 170 | 204 | 715 |
| San Luis Obispo | 45,119 | 38,117 | 523 | 275 | 2,350 | 65 | 1,973 | 1,816 | 6,626 |
| Census-designated places | Total Population | White | African American | Native American | Asian | Pacific Islander | other races | two or more races | Hispanic or Latino (of any race) |
| Avila Beach | 1,627 | 1,507 | 13 | 7 | 33 | 0 | 34 | 33 | 111 |
| Blacklake | 930 | 865 | 8 | 7 | 24 | 0 | 14 | 12 | 70 |
| Callender | 1,262 | 1,003 | 7 | 22 | 48 | 0 | 128 | 54 | 355 |
| Cambria | 6,032 | 5,166 | 18 | 47 | 78 | 14 | 557 | 152 | 1,187 |
| Cayucos | 2,592 | 2,366 | 6 | 12 | 54 | 8 | 57 | 89 | 207 |
| Creston | 94 | 89 | 0 | 2 | 1 | 0 | 0 | 2 | 6 |
| Edna | 193 | 185 | 0 | 3 | 0 | 0 | 5 | 0 | 22 |
| Garden Farms | 386 | 348 | 2 | 2 | 5 | 0 | 21 | 8 | 40 |
| Lake Nacimiento | 2,411 | 2,153 | 12 | 44 | 24 | 5 | 75 | 98 | 256 |
| Los Berros | 641 | 527 | 4 | 1 | 12 | 1 | 45 | 51 | 153 |
| Los Osos | 14,276 | 12,304 | 79 | 97 | 748 | 18 | 552 | 478 | 1,977 |
| Los Ranchos | 1,477 | 1,389 | 1 | 2 | 31 | 0 | 18 | 36 | 58 |
| Nipomo | 16,714 | 12,281 | 177 | 200 | 421 | 33 | 2,821 | 781 | 6,645 |
| Oak Shores | 337 | 318 | 3 | 2 | 4 | 0 | 4 | 6 | 31 |
| Oceano | 7,286 | 5,105 | 62 | 120 | 165 | 7 | 1,509 | 318 | 3,484 |
| San Miguel | 2,336 | 1,638 | 65 | 58 | 19 | 1 | 474 | 81 | 1,196 |
| San Simeon | 462 | 270 | 4 | 5 | 9 | 2 | 160 | 12 | 258 |
| Santa Margarita | 1,259 | 1,077 | 8 | 28 | 34 | 0 | 42 | 70 | 206 |
| Shandon | 1,295 | 840 | 34 | 18 | 7 | 2 | 352 | 42 | 693 |
| Templeton | 7,674 | 6,833 | 59 | 80 | 123 | 10 | 337 | 232 | 1,171 |
| Whitley Gardens | 285 | 260 | 1 | 6 | 1 | 0 | 13 | 4 | 43 |
| Woodlands | 576 | 541 | 7 | 0 | 18 | 1 | 3 | 6 | 27 |
| Other unincorporated areas | Total Population | White | African American | Native American | Asian | Pacific Islander | other races | two or more races | Hispanic or Latino (of any race) |
| All others not CDPs (combined) | 47,973 | 39,400 | 2,854 | 462 | 1,422 | 40 | 2,250 | 1,545 | 7,659 |

### 2000 Census

As of the census of 2000, there were 246,681 residents, 92,739 households, and 58,611 families in the county. The population density was 75 people per square mile (29 people/km$^2$). There were 102,275 housing units at an average density of 31 units per square mile (12 units/km$^2$). The racial makeup of the county was 84.6% White, 2.0% Black or African American, 1.0% Native American, 2.7% Asian, 0.1% Pacific Islander, 6.2% from other races, and 3.4% from two or more races. 16.3% of the population were Hispanic or Latino of any race. 13.9% were of German, 11.4% English, 9.7% Irish, 6.1% American and 5.7% Italian ancestry according to Census 2000. 85.7% spoke English and 10.7% Spanish as their first language.
There were 92,739 households, out of which 28.2% had children under the age of 18 living with them, 50.40% were married couples living together, 9.1% had a female householder with no husband present, and 36.8% were non-families. 26.0% of all households were made up of individuals, and 10.3% had someone living alone who was 65 years of age or older. The average household size was 2.49 and the average family size was 3.01.
In the county, the population was spread out, with 21.7% under the age of 18, 13.6% from 18 to 24, 27.0% from 25 to 44, 23.3% from 45 to 64, and 14.5% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 105.6 males. For every 100 females age 18 and over, there were 105.2 males.
The median income for a household in the county was $42,428, and the median income for a family was $52,447. Males had a median income of $40,726 versus $27,450 for females. The per capita income for the county was $21,864. About 6.8% of families and 12.8% of the population were below the poverty line, including 11.4% of those under age 18 and 5.9% of those age 65 or over.

## Economy

The mainstays of the economy are California Polytechnic State University with its almost 20,000 students, tourism, and agriculture. The economic indicators reveal that San Luis Obispo County aligns closely with California regarding median household income and poverty rates. However, the county distinguishes itself through higher educational attainment and homeownership rates, alongside a distinctive employment sector composition favoring agriculture and related industries. Despite these strengths, the county is not immune to challenges, as evidenced by a housing market that is significantly more expensive than the rest of California and growing income inequality. San Luis Obispo County's economy is primarily a service economy. Service jobs account for 38% of the county's jobs, government jobs accounts for 20.7%, and manufacturing jobs represent 6% of the county's jobs.
San Luis Obispo County is the third largest producer of wine in California, surpassed only by Sonoma and Napa counties. Wine grapes are the second largest agricultural crop in the county (after strawberries), and the wine production they support creates a direct economic impact and a growing wine country vacation industry.
The county led the state in hemp cultivation in 2018 as hundreds of acres of the crop were grown in research partnerships. In 2019, nine agricultural research permits were still active. Sixteen commercial permits were issued before a temporary ban on new applications running through June 2020 was passed by the Board of Supervisors.

## Politics
### Voter registration

Population and registered voters :
| Total population | 267,871 | 267,871 |
| Registered voters | 184,744 | 58.4% |
| Democratic | 70,180 | 38% |
| Republican | 63,687 | 34.5% |
| Democratic–Republican spread | +6,493 | +3.5% |
| American Independent | 7,116 | 3.9% |
| Green | 972 | 0.5% |
| Libertarian | 2,401 | 1.3% |
| Peace and Freedom | 566 | 0.3% |
| Other | 1,752 | 1% |
| No party preference | 37,366 | 20.2% |

#### Cities by population and voter registration

Cities by population and voter registration :
| City | Population | Registered voters | Democratic | Republican | D–R spread | Other | No party preference |
| Arroyo Grande | 17,132 | 65.5% | 34.2% | 41.8% | -7.6% | 8.1% | 18.7% |
| Atascadero | 28,194 | 58.9% | 30.8% | 43.9% | -13.1% | 8.2% | 19.8% |
| El Paso de Robles (Paso Robles) | 29,270 | 52.1% | 29.6% | 45.3% | -15.7% | 8.2% | 19.9% |
| Grover Beach | 13,175 | 50.6% | 37.3% | 34.0% | +3.3% | 9.3% | 22.5% |
| Morro Bay | 10,263 | 68.4% | 39.5% | 31.6% | +7.9% | 9.5% | 22.2% |
| Pismo Beach | 7,753 | 70.4% | 32.2% | 41.5% | -9.3% | 8.9% | 20.3% |
| San Luis Obispo | 45,130 | 59.2% | 40.0% | 29.1% | +10.9% | 9.0% | 24.6% |

### Overview

San Luis Obispo County leaned toward the Republican Party in presidential and congressional elections during most of the 20th century; it has, however, become more Democratic starting in the 2000s. In 2008, Barack Obama won the county with 51.2 percent of the vote. Prior to 2008, the last Democrat to win a majority in the county was Lyndon B. Johnson in 1964, although Bill Clinton won a plurality in 1992. In 2012, Obama again won the county, this time with a slim plurality of the vote. Hillary Clinton won with a larger plurality in 2016; and in 2020, Joe Biden won a solid 55% of the vote, the largest for any Democrat since Johnson.
United States presidential election results for San Luis Obispo County, California :
| Year | Republican | Republican | Democratic | Democratic | Third party(ies) | Third party(ies) |
| Year | No. | % | No. | % | No. | % |
| 2024 | 64,932 | 43.05% | 81,314 | 53.92% | 4,566 | 3.03% |
| 2020 | 67,436 | 42.22% | 88,310 | 55.29% | 3,968 | 2.48% |
| 2016 | 56,164 | 40.94% | 67,107 | 48.91% | 13,931 | 10.15% |
| 2012 | 59,967 | 47.61% | 61,258 | 48.63% | 4,741 | 3.76% |
| 2008 | 61,055 | 45.85% | 68,176 | 51.20% | 3,924 | 2.95% |
| 2004 | 67,995 | 52.69% | 58,742 | 45.52% | 2,313 | 1.79% |
| 2000 | 56,859 | 52.22% | 44,526 | 40.89% | 7,501 | 6.89% |
| 1996 | 46,733 | 46.50% | 40,395 | 40.19% | 13,372 | 13.31% |
| 1992 | 36,384 | 34.78% | 40,136 | 38.36% | 28,099 | 26.86% |
| 1988 | 46,613 | 55.85% | 35,667 | 42.73% | 1,187 | 1.42% |
| 1984 | 49,035 | 63.72% | 26,946 | 35.02% | 969 | 1.26% |
| 1980 | 38,631 | 55.56% | 20,508 | 29.50% | 10,388 | 14.94% |
| 1976 | 27,785 | 51.17% | 24,926 | 45.91% | 1,587 | 2.92% |
| 1972 | 28,566 | 55.98% | 20,779 | 40.72% | 1,688 | 3.31% |
| 1968 | 19,420 | 51.27% | 15,828 | 41.78% | 2,633 | 6.95% |
| 1964 | 14,906 | 40.08% | 22,252 | 59.84% | 28 | 0.08% |
| 1960 | 17,862 | 54.04% | 14,975 | 45.30% | 218 | 0.66% |
| 1956 | 16,223 | 58.47% | 11,407 | 41.11% | 118 | 0.43% |
| 1952 | 17,716 | 65.37% | 9,174 | 33.85% | 213 | 0.79% |
| 1948 | 10,325 | 53.49% | 8,135 | 42.14% | 844 | 4.37% |
| 1944 | 7,793 | 48.90% | 8,068 | 50.63% | 75 | 0.47% |
| 1940 | 7,204 | 45.25% | 8,499 | 53.39% | 217 | 1.36% |
| 1936 | 4,812 | 37.28% | 7,889 | 61.13% | 205 | 1.59% |
| 1932 | 3,449 | 28.59% | 7,933 | 65.77% | 680 | 5.64% |
| 1928 | 5,425 | 60.82% | 3,336 | 37.40% | 159 | 1.78% |
| 1924 | 3,804 | 49.01% | 731 | 9.42% | 3,226 | 41.57% |
| 1920 | 4,123 | 61.31% | 1,606 | 23.88% | 996 | 14.81% |
| 1916 | 2,854 | 40.20% | 3,539 | 49.85% | 706 | 9.95% |
| 1912 | 13 | 0.23% | 2,248 | 40.48% | 3,292 | 59.28% |
| 1908 | 2,008 | 50.76% | 1,381 | 34.91% | 567 | 14.33% |
| 1904 | 2,015 | 54.95% | 1,167 | 31.82% | 485 | 13.23% |
| 1900 | 1,564 | 45.81% | 1,713 | 50.18% | 137 | 4.01% |
| 1896 | 1,671 | 43.74% | 2,056 | 53.82% | 93 | 2.43% |
| 1892 | 1,433 | 38.10% | 1,199 | 31.88% | 1,129 | 30.02% |
| 1888 | 1,689 | 49.68% | 1,585 | 46.62% | 126 | 3.71% |
| 1884 | 1,233 | 51.44% | 1,069 | 44.60% | 95 | 3.96% |
| 1880 | 830 | 47.81% | 729 | 41.99% | 177 | 10.20% |
With respect to the United States House of Representatives, San Luis Obispo County is mostly in California's 24th congressional district, represented by Democrat Salud Carbajal, with the northern part of the county in California's 19th congressional district, represented by Democrat Jimmy Panetta. From 2003 until 2013, the county was split between the Bakersfield-based 22nd district, which was represented by Republican Kevin McCarthy and included Paso Robles and most of the more conservative inland areas of the county, and Lois Capps' 23rd district, a strip which included most of the county's more liberal coastal areas as well as coastal areas of Santa Barbara and Ventura counties.
With respect to the California State Senate, the county is in the 17th Senate District, represented by Democrat John Laird. With respect to the California State Assembly, the county is in the 30th Assembly District, represented by Democrat Dawn Addis.
In April 2008, the California Secretary of State reported that there were 147,326 registered voters in San Luis Obispo County. Of those voters, 61,226 (41.6%) were registered Republicans, 52,586 (35.7%) were registered Democratic, 8,030 (5.4%) are registered with other political parties, and 25,484 (17.3%) declined to state a political preference. The cities of Grover Beach, Morro Bay, and San Luis Obispo had pluralities or majorities of registered Democratic voters, whereas the rest of the county's towns, cities, and the unincorporated areas have a plurality or majority of registered Republican voters.

## Crime

The following table includes the number of incidents reported and the rate per 1,000 persons for each type of offense.
Population and crime rates :
| Population | 267,871 | 267,871 |
| Violent crime | 694 | 2.59 |
| Homicide | 4 | 0.01 |
| Forcible rape | 89 | 0.33 |
| Robbery | 106 | 0.40 |
| Aggravated assault | 495 | 1.85 |
| Property crime | 3,009 | 11.23 |
| Burglary | 1,433 | 5.35 |
| Larceny-theft | 4,169 | 15.56 |
| Motor vehicle theft | 375 | 1.40 |
| Arson | 88 | 0.33 |

### Cities by population and crime rates

Cities by population and crime rates :
| City | Population | Violent crimes | Violent crime rate per 1,000 persons | Property crimes | Property crime rate per 1,000 persons |
| Arroyo Grande | 17,568 | 60 | 3.42 | 358 | 20.38 |
| Atascadero | 28,825 | 192 | 6.66 | 658 | 22.83 |
| Grover Beach | 13,398 | 32 | 2.39 | 306 | 22.84 |
| Morro Bay | 10,423 | 21 | 2.01 | 140 | 13.43 |
| Paso Robles | 30,344 | 91 | 3.00 | 777 | 25.61 |
| Pismo Beach | 7,798 | 36 | 4.62 | 305 | 39.11 |
| San Luis Obispo | 45,947 | 119 | 2.59 | 1,971 | 42.90 |

## Fire protection

In unincorporated parts of the county, fire protection and emergency response services have been provided by the San Luis Obispo County Fire Department, through a cooperative agreement with CAL FIRE, since 1930. The county fire department also serves Los Osos, Oceano, and Avila Beach. The city of San Luis Obispo is served by the San Luis Obispo City Fire Department.

## Transportation
### Major highways

* U.S. Route 101
* State Route 1
* State Route 33
* State Route 41
* State Route 46
* State Route 58
* State Route 166
* State Route 227
* State Route 229

### Public transportation

San Luis Obispo County is served by Amtrak trains and Greyhound Lines buses. The San Luis Obispo Regional Transit Authority provides countywide service along US 101 as well as service to Morro Bay, Los Osos, Cambria and San Simeon.
The cities of San Luis Obispo, Atascadero and Paso Robles operate their own local bus services; all of these connect with SLORTA routes.
Intercity service is provided by Amtrak trains, Greyhound Lines and Orange Belt Stages buses.
The Amtrak Thruway 18 provides a daily connection to Visalia on the east, and Santa Maria on the west, with several stops in between.
FlixBus boards from the San Luis Obispo Railroad Museum at 1940 Santa Barbara Avenue.

### Airports

* San Luis Obispo County Regional Airport (SBP) is located just south of the City of San Luis Obispo. Commercial flights are available.
* Paso Robles Municipal Airport (PRB) is located north-east of the City of Paso Robles and is home to California Highway Patrol, CAL-FIRE and the Estrella Warbirds Museum.
* Oceano County Airport (L52) is located on the coast in the 5 Cities area.

### Future

In the future, SR 46 may be considered for a possible westward expansion of Interstate 40 via SR 58 from Barstow to Bakersfield, from Bakersfield to I-5 via Westside Parkway, and then following SR 46 to Paso Robles. SR 46 is slowly being upgraded to Interstate standards, minus overpasses between Interstate 5 and US Route 101.

## Communities
### Cities

* Arroyo Grande
* Atascadero
* Grover Beach
* Morro Bay
* Paso Robles
* Pismo Beach
* San Luis Obispo (county seat)

### Unincorporated communities

* Avila Beach
* Baywood Park
* Blacklake
* California Polytechnic State University
* California Valley
* Callender
* Cambria
* Cayucos
* Creston
* Cholame
* Edna
* Garden Farms
* Halcyon
* Harmony
* Lake Nacimiento
* Los Berros
* Los Osos
* Los Ranchos
* Nipomo
* Oak Shores
* Oceano
* Pozo
* San Miguel
* San Simeon
* Santa Margarita
* Shandon
* Templeton
* Whitley Gardens
* Woodlands

### Population ranking

The population ranking of the following table is based on the 2020 census of San Luis Obispo County.
† county seat
| Rank | City/Town/etc. | Municipal type | Population (2020 Census) |
| 1 | † San Luis Obispo | City | 47,063 |
| 2 | Paso Robles (El Paso de Robles) | City | 31,490 |
| 3 | Atascadero | City | 29,773 |
| 4 | Arroyo Grande | City | 18,441 |
| 5 | Nipomo | CDP | 18,176 |
| 6 | Los Osos | CDP | 14,465 |
| 7 | Grover Beach | City | 12,701 |
| 8 | Morro Bay | City | 10,757 |
| 9 | Templeton | CDP | 8,386 |
| 10 | Pismo Beach | City | 8,072 |
| 11 | Oceano | CDP | 7,183 |
| 12 | Cambria | CDP | 5,678 |
| 13 | San Miguel | CDP | 3,172 |
| 14 | Lake Nacimiento | CDP | 2,956 |
| 15 | Cayucos | CDP | 2,505 |
| 16 | Woodlands | CDP | 1,933 |
| 17 | Avila Beach | CDP | 1,576 |
| 18 | Los Ranchos | CDP | 1,516 |
| 19 | Santa Margarita | CDP | 1,291 |
| 20 | Callender | CDP | 1,282 |
| 21 | Shandon | CDP | 1,168 |
| 22 | Blacklake | CDP | 1,016 |
| 23 | Los Berros | CDP | 623 |
| 24 | Garden Farms | CDP | 449 |
| 25 | San Simeon | CDP | 445 |
| 26 | Whitley Gardens | CDP | 325 |
| 27 | Oak Shores | CDP | 316 |
| 28 | Edna | CDP | 184 |
| 29 | Creston | CDP | 98 |