Originally part of Mexico, California became a U.S. state in 1850 following the Gold Rush, which dramatically increased its population. California is a key economic powerhouse today. It has 58 counties.
10 Largest Counties in California
1. Los Angeles County
County Facts
- Population: 10,014,009 (2020 Census)
- Area Codes: 213, 310, 323, 424, 562, 626, 661, 747, 818, 909
- ZIP Codes: 90001-93599
- County Seat: Los Angeles
Geography and History
Los Angeles County, located in southern California, spans 4,753 square miles and includes coastal areas, mountain ranges, and urban sprawls. The county is bordered by the Pacific Ocean to the west and the San Gabriel and San Bernardino Mountains to the north and east. Established in 1850, Los Angeles County rapidly developed from a small pueblo to one of the most populous regions in the world. Its diverse economy was initially based on agriculture and oil, but by the early 20th century, Hollywood made Los Angeles a global center for the entertainment industry. In addition to film, aerospace, technology, and trade have played major roles in the county’s growth. The county is known for its diversity, with a wide range of cultures and languages represented.
Colleges and Universities
- University of California, Los Angeles (UCLA): A prestigious public research university known for its programs in law, medicine, and engineering.
- University of Southern California (USC): A private research university with a strong focus on film, business, and engineering.
- California State University, Los Angeles (CSULA): Offers a variety of undergraduate and graduate programs with a strong focus on public service and education.
- California Institute of Technology (Caltech): A world-renowned private university specializing in science and engineering.
Major Landmarks
Los Angeles County is home to globally recognized landmarks like Hollywood, the center of the film industry, and Griffith Observatory, offering stunning views of the city and the stars. Santa Monica Pier and Venice Beach are iconic coastal destinations, while The Getty Center houses an extensive art collection. Universal Studios Hollywood and Disneyland in nearby Orange County are popular theme parks. Los Angeles County Museum of Art (LACMA) is the largest art museum in the western U.S., and the Walt Disney Concert Hall is an architectural marvel and performance venue.
2. San Diego County
County Facts
- Population: 3,298,634 (2020 Census)
- Area Codes: 619, 858, 760
- ZIP Codes: 91901-92199
- County Seat: San Diego
Geography and History
San Diego County is located in southern California, bordering Mexico, the Pacific Ocean, and the desert regions to the east. Covering 4,526 square miles, it has a diverse landscape, from coastal beaches to mountains and deserts. San Diego was the first European settlement on the West Coast, established by the Spanish in 1769. The area became part of the U.S. in 1848 after the Mexican-American War. The county’s economy historically revolved around military and defense industries due to its strategic port location. Today, biotechnology, tourism, and telecommunications also play significant roles in the local economy. San Diego’s climate and natural beauty make it a popular destination for residents and tourists alike.
Colleges and Universities
- University of California, San Diego (UCSD): A top public research university known for its programs in medicine, oceanography, and engineering.
- San Diego State University (SDSU): A public university with a strong reputation in business, public administration, and the arts.
- University of San Diego (USD): A private Roman Catholic university with notable programs in law, business, and education.
- Point Loma Nazarene University: A private Christian university focused on liberal arts and religious studies.
Major Landmarks
San Diego County features iconic landmarks such as Balboa Park, which includes the San Diego Zoo, museums, and gardens. Old Town San Diego State Historic Park preserves early California history, while Cabrillo National Monument offers views of the Pacific Ocean and honors explorer Juan Rodriguez Cabrillo. La Jolla Cove is famous for its beaches and marine life, and USS Midway Museum is a historic aircraft carrier now serving as a maritime museum. The Gaslamp Quarter in downtown San Diego is known for its nightlife, and Torrey Pines State Natural Reserve offers hiking and spectacular ocean views.
3. Orange County
County Facts
- Population: 3,186,989 (2020 Census)
- Area Codes: 714, 949
- ZIP Codes: 92602-92899
- County Seat: Santa Ana
Geography and History
Orange County is located between Los Angeles and San Diego counties, covering 948 square miles of coastal plains and hills. Known for its affluent communities and extensive suburban development, Orange County was primarily agricultural—focused on citrus orchards—before suburbanization exploded in the mid-20th century. Founded in 1889, it rapidly grew as a result of post-World War II economic booms and became a major center for aerospace, defense, and tourism. Today, tourism, technology, and finance drive the local economy. Its coastal cities, such as Newport Beach and Laguna Beach, are popular destinations, and it is also home to some of the nation’s most famous theme parks.
Colleges and Universities
- University of California, Irvine (UCI): A public research university known for its medical and engineering programs.
- Chapman University: A private university with strengths in film, law, and business.
- California State University, Fullerton (CSUF): A large public university offering a wide range of undergraduate and graduate programs.
- Concordia University Irvine: A private Christian university focusing on liberal arts and religious studies.
Major Landmarks
Orange County is internationally recognized for Disneyland Resort, one of the world’s most visited theme parks. Knott’s Berry Farm is another popular amusement park with a rich history. Mission San Juan Capistrano, one of California’s historic Spanish missions, attracts visitors for its architecture and cultural significance. Coastal destinations such as Huntington Beach, known as “Surf City USA,” and Newport Harbor provide scenic beauty and recreational opportunities. Crystal Cove State Park offers hiking and beach access, while the Bowers Museum in Santa Ana highlights cultural art from around the world.
4. Riverside County
County Facts
- Population: 2,418,185 (2020 Census)
- Area Codes: 951, 760
- ZIP Codes: 91752-92596
- County Seat: Riverside
Geography and History
Riverside County is one of California’s largest counties by area, covering 7,208 square miles of diverse terrain, from the Inland Empire’s urban centers to desert regions in the Coachella Valley. The county was established in 1893, carved from parts of San Bernardino and San Diego counties. Riverside’s economy initially focused on agriculture, particularly citrus farming, which gave rise to the city of Riverside as a major center for the citrus industry. Today, the county’s economy is driven by logistics, agriculture, tourism, and a growing suburban population. Its desert areas, including Palm Springs and Joshua Tree National Park, are major tourist destinations.
Colleges and Universities
- University of California, Riverside (UCR): A public research university with strengths in agriculture, science, and public policy.
- California Baptist University: A private Christian university offering undergraduate and graduate programs in health sciences, business, and the arts.
- Riverside Community College District: Offers associate degrees and vocational training across multiple campuses.
- La Sierra University: A private Seventh-day Adventist university focusing on liberal arts and religious education.
Major Landmarks
Riverside County boasts natural landmarks like Joshua Tree National Park, famous for its unique desert flora and rock formations, and Mount San Jacinto State Park, accessible by the Palm Springs Aerial Tramway. The Mission Inn Hotel & Spa in Riverside is a historical landmark known for its eclectic architecture. Coachella Valley hosts the famous Coachella Music and Arts Festival, while Palm Springs is renowned for its mid-century modern architecture and resorts. Lake Perris State Recreation Area offers camping and water sports, and Riverside’s Citrus State Historic Park commemorates the county’s agricultural heritage.
5. San Bernardino County
County Facts
- Population: 2,181,654 (2020 Census)
- Area Codes: 909, 760, 442
- ZIP Codes: 91701-93592
- County Seat: San Bernardino
Geography and History
San Bernardino County is the largest county by area in the United States, covering a vast 20,105 square miles, stretching from urban areas to desert landscapes. The county includes parts of the Mojave Desert, the San Bernardino Mountains, and the Colorado River. Established in 1853, it grew rapidly due to the development of the Santa Fe Railroad and its strategic location along the old Route 66. Historically, agriculture and mining were key industries, but the county’s economy diversified into logistics, manufacturing, and aerospace as its population surged. Today, it remains a significant transportation hub due to its location along major interstate highways.
Colleges and Universities
- California State University, San Bernardino (CSUSB): A public university known for its business, public administration, and education programs.
- University of Redlands: A private liberal arts university offering programs in business, education, and the arts.
- San Bernardino Valley College: A community college providing associate degrees and vocational programs.
- Chaffey College: A community college with a strong focus on transfer degrees and technical education.
Major Landmarks
San Bernardino County is home to natural wonders like Big Bear Lake, a popular year-round destination for skiing, hiking, and boating, and Mojave National Preserve, which offers sweeping desert landscapes and historic sites. Route 66 passes through many of the county’s cities, with landmarks such as the Wigwam Motel in Rialto. The California Theatre of the Performing Arts in San Bernardino is a historical venue for cultural events. Joshua Tree National Park also extends into the county, offering iconic desert vistas. Ontario Mills Mall is one of the largest outlet shopping centers in the state, and Glen Helen Amphitheater hosts major concerts and events.
6. Santa Clara County
County Facts
- Population: 1,936,259 (2020 Census)
- Area Codes: 408, 669
- ZIP Codes: 94022-95196
- County Seat: San Jose
Geography and History
Santa Clara County, located in the heart of Silicon Valley, spans 1,304 square miles in northern California. The region’s geography includes the Santa Cruz Mountains to the west and the Diablo Range to the east, with the fertile Santa Clara Valley in between. Historically an agricultural center known for orchards and vineyards, the county’s economy transformed with the rise of the technology industry in the late 20th century. The presence of companies like Apple, Google, and Intel turned Santa Clara County into a global tech hub. Established in 1850, San Jose is California’s oldest civil settlement and grew into a major city alongside the development of Silicon Valley.
Colleges and Universities
- Stanford University: A world-renowned private university known for its programs in business, engineering, and the sciences.
- Santa Clara University: A private Jesuit university offering strong programs in law, business, and engineering.
- San Jose State University (SJSU): A public university known for its programs in engineering, business, and education.
- Foothill-De Anza Community College District: One of the top community college districts in the U.S., offering transfer programs to four-year universities.
Major Landmarks
Santa Clara County is home to Silicon Valley, the global center of the technology industry. Stanford University’s campus in Palo Alto is a major landmark, known for its architecture and research institutions. Winchester Mystery House in San Jose attracts visitors for its unique and eerie architecture. Tech Interactive in downtown San Jose is a science and technology museum. Levi’s Stadium, home to the San Francisco 49ers, hosts major sporting events and concerts. Villa Montalvo in Saratoga is an arts center and historic landmark, while Alum Rock Park offers scenic hiking trails and natural mineral springs.
7. Alameda County
County Facts
- Population: 1,682,353 (2020 Census)
- Area Codes: 510, 341, 925
- ZIP Codes: 94501-94720
- County Seat: Oakland
Geography and History
Alameda County is located in the San Francisco Bay Area, covering 821 square miles of coastal plains, hills, and urban centers. The county includes the cities of Oakland, Berkeley, and Fremont, and is known for its diverse population and industries. Established in 1853, the county’s economy was historically based on agriculture and shipping, but industrial growth during World War II turned Oakland into a major port city. In the post-war era, Alameda County became a hub for higher education, healthcare, and technology. Today, the county is known for its cultural diversity, progressive politics, and vibrant arts scene.
Colleges and Universities
- University of California, Berkeley (UC Berkeley): One of the top public universities in the world, known for its programs in science, engineering, and the humanities.
- California State University, East Bay (CSUEB): A public university with strengths in business, education, and health sciences.
- Mills College: A private liberal arts college offering undergraduate programs for women and graduate programs for both men and women.
- Chabot College: A community college in Hayward offering vocational training and associate degrees.
Major Landmarks
Alameda County is home to famous landmarks like UC Berkeley, one of the world’s leading research universities, and Oakland Museum of California, which offers exhibits on art, history, and natural sciences. Lake Merritt in Oakland is a popular spot for outdoor recreation and wildlife viewing. Chabot Space and Science Center provides educational exhibits and observatories for stargazing. Jack London Square along Oakland’s waterfront is a historic and cultural destination. Tilden Regional Park in Berkeley offers hiking, a botanic garden, and a vintage carousel. O.co Coliseum and RingCentral Coliseum are major venues for professional sports and concerts.
8. Sacramento County
County Facts
- Population: 1,585,055 (2020 Census)
- Area Codes: 916, 279
- ZIP Codes: 94203-95899
- County Seat: Sacramento
Geography and History
Sacramento County, located in California’s Central Valley, covers 994 square miles and is centered around the Sacramento River. The county was established in 1850 and played a vital role in the California Gold Rush, becoming a hub for settlers and entrepreneurs. Sacramento became the state capital in 1854, and the county grew rapidly with the development of the transcontinental railroad and agriculture, particularly rice and fruit crops. Today, Sacramento County’s economy is driven by government services, healthcare, and agriculture, with technology and education also playing key roles.
Colleges and Universities
- California State University, Sacramento (Sacramento State): A public university offering programs in business, education, engineering, and health sciences.
- University of California, Davis (UC Davis): Located nearby in Yolo County, UC Davis serves many Sacramento County residents and is known for its programs in agriculture, veterinary medicine, and environmental sciences.
- Sacramento City College: A community college providing associate degrees, vocational training, and transfer programs.
- Los Rios Community College District: A network of community colleges serving the Sacramento area, including American River College and Cosumnes River College.
Major Landmarks
Sacramento County is known for the California State Capitol, the center of state government, and Old Sacramento, a historic district preserving the Gold Rush era with museums, shops, and restaurants. The Crocker Art Museum is the oldest art museum in the West, housing significant collections of art. Sutter’s Fort is a preserved 19th-century trading post, while the California State Railroad Museum offers a glimpse into the history of railroads in the West. The Sacramento Zoo and American River Parkway provide outdoor recreation, while Golden 1 Center is home to the Sacramento Kings and hosts major concerts and events.
9. Fresno County
County Facts
- Population: 1,008,654 (2020 Census)
- Area Codes: 559
- ZIP Codes: 93210-93888
- County Seat: Fresno
Geography and History
Fresno County is located in the heart of California’s Central Valley, covering 6,011 square miles of farmland, foothills, and mountains. The county is one of the most productive agricultural regions in the world, growing crops like grapes, almonds, and citrus. Fresno County was established in 1856, and its economy has long revolved around agriculture, supported by an extensive irrigation network. The county seat, Fresno, grew from a railway station in the late 19th century to become a major city. While agriculture remains central to the economy, Fresno County has also developed industries in healthcare, education, and logistics.
Colleges and Universities
- California State University, Fresno (Fresno State): A public university known for its agricultural, business, and engineering programs.
- Fresno City College: A community college offering associate degrees, vocational training, and transfer programs.
- San Joaquin College of Law: A private law school located in Clovis, offering legal education for Central Valley residents.
- Fresno Pacific University: A private Christian university with programs in education, business, and the liberal arts.
Major Landmarks
Fresno County is home to Yosemite National Park, with its stunning landscapes of waterfalls, cliffs, and giant sequoias. Kings Canyon National Park and Sequoia National Park are also partially located within the county, offering outdoor adventures. Forestiere Underground Gardens in Fresno is an architectural marvel of subterranean tunnels and gardens. Chaffee Zoo in Fresno is a family-friendly destination, and the Fresno Art Museum showcases local and international artists. Woodward Park offers scenic trails and a Japanese garden, while Fresno’s Tower District is known for its historic theater and vibrant nightlife.
10. Contra Costa County
County Facts
- Population: 1,165,927 (2020 Census)
- Area Codes: 925, 510
- ZIP Codes: 94505-94850
- County Seat: Martinez
Geography and History
Contra Costa County is located in the San Francisco Bay Area, covering 804 square miles of coastal and inland areas. The county is bordered by the San Francisco Bay to the west and the Sacramento River to the north. Contra Costa was established in 1850 and played a key role in the early shipping and industrial development of the Bay Area. The discovery of oil in the late 19th century spurred growth in refineries and shipping industries. Today, the county’s economy is diverse, with industries in technology, healthcare, and education driving growth.
Colleges and Universities
- California State University, East Bay (CSUEB-Concord Campus): Offers undergraduate and graduate programs with a focus on business, education, and health sciences.
- Saint Mary’s College of California: A private Catholic university in Moraga offering programs in liberal arts, business, and education.
- Contra Costa College: A community college providing vocational training, associate degrees, and transfer opportunities.
- Diablo Valley College: Another major community college in the region known for its transfer programs to four-year universities.
Major Landmarks
Contra Costa County features scenic natural landmarks like Mount Diablo, known for its panoramic views of the Bay Area. John Muir National Historic Site preserves the home of the famed naturalist, while Black Diamond Mines Regional Preserve offers hiking trails and a glimpse into the county’s mining history. Lindsay Wildlife Experience in Walnut Creek is an educational center focused on local wildlife. Martinez Regional Shoreline provides waterfront parks and trails, and Briones Regional Park offers hiking and wildlife viewing opportunities. The Ruth Bancroft Garden in Walnut Creek is known for its drought-tolerant plants, and Concord Pavilion is a popular outdoor concert venue.