San Diego County, California

San Diego County is a county in California, United States, in the state’s southwest corner about 120 miles south of Los Angeles and directly north of the Mexican border at Tijuana. It had a population of 3,298,634 at the 2020 census, an estimated 3,298,799 by 2024, and covers 4,207 square miles (10,899 km2) of land centred near 33°01′N 116°46′W.

San Diego is the county seat and California’s second-most populous city; its main postal code is 92101. The county holds 18 incorporated cities and dozens of unincorporated communities — California has no civil townships — and it runs on Pacific time. Its FIPS code is 06073.

Towns & Villages in San Diego County

San Diego County has 18 incorporated cities, from the 1.38-million-resident city of San Diego down to Del Mar’s 3,949 residents. Every incorporated place in California is legally a “city” — there is no separate “town” classification — so the table below uses City for all 18 and marks the county seat.

Coronado is a city on a peninsula, not the naval air station of the same name that sits within its limits, and Del Mar — the county’s smallest city by population — is not the Del Mar Fairgrounds, which is unincorporated county land next door.

Unincorporated Communities

Outside the 18 cities, San Diego County recognizes at least 37 census-designated places (CDPs) — unincorporated communities the Census Bureau tracks for statistics but that have no city government of their own. The 18 largest, all with a 2020 census count, are below; the rest are smaller mountain, desert and backcountry communities such as Descanso, Guatay, Pala, Palomar Mountain, Ranchita and Warner Springs, most under 1,000 residents and without a separate CDP population of their own.

Winter Gardens and Lakeside share the 92040 ZIP, and Casa de Oro-Mount Helix shares La Mesa’s 91941, which is why the same code appears twice in the tables above.

ZIP Codes

• 92101 — San Diego (downtown; the city itself carries dozens more)
• 91910 — Chula Vista
• 92054 — Oceanside
• 92025 — Escondido
• 92008 — Carlsbad
• 92020 — El Cajon
• 92084 — Vista
• 92069 — San Marcos
• 92028 — Fallbrook (also serves De Luz and Rainbow)
• 91977 — Spring Valley (also serves Casa de Oro-Mount Helix)
• 92065 — Ramona
• 92040 — Lakeside (also serves Winter Gardens and Eucalyptus Hills)
• 91901 — Alpine
• 91902 — Bonita
• 92082 — Valley Center
• 91935 — Jamul
• 92003 — Bonsall
• 92004 — Borrego Springs
• 92036 — Julian
• 91962 — Pine Valley

San Diego County has roughly 90 ZIP codes in all — the county’s big cities each carry several, and the county overall is one of the most ZIP-dense in California.

Geography

San Diego County runs from Pacific beaches through coastal mesas and inland foothills to the 6,500-foot Cuyamaca and Laguna mountain ranges, then drops into the Anza-Borrego Desert basin in the east. Of its 4,526 square miles of total area, 4,207 square miles are land and about 319 square miles are water, most of that the coastal Pacific within the county’s jurisdiction plus reservoirs such as San Vicente and El Capitan. The San Diego River is the county’s principal waterway, running about 52 miles from the Cuyamaca Mountains to Mission Bay.

San Diego County borders Orange County and Riverside County to the north, Imperial County to the east, the Pacific Ocean to the west, and Mexico — the Tijuana and Tecate municipalities of Baja California — to the south.

Demographics

San Diego County had a population of 3,298,634 at the 2020 census and an estimated 3,298,799 by 2024, holding steady as California’s second-most populous county and the nation’s fifth. San Diego (1,384,481) and Chula Vista (275,503) are its two largest communities. Median household income is $102,285, about 7% above California’s $96,334 statewide figure. Density works out to roughly 784 people per square mile of land.

Economy & Local Life

The U.S. Navy is the county’s largest employer, with more than 41,600 civilian and military positions at Naval Base San Diego, and the county hosts roughly 110,000 active-duty personnel overall. UC San Diego employs over 38,700, and Sharp HealthCare over 19,000. Hospitality and tourism account for more than 67,500 jobs. San Diego markets itself as the “Craft Beer Capital of America,” with dozens of breweries concentrated in and around the city, and the county is a top U.S. producer of avocados and nursery crops, an agricultural sector worth roughly $1.85 billion a year. Notable institutions include UC San Diego, San Diego State University, the Salk Institute, Scripps Research, the USS Midway Museum and Balboa Park’s museum and zoo complex. The county’s biggest annual events are the San Diego County Fair at the Del Mar Fairgrounds each June and Comic-Con International in downtown San Diego each July.

History

San Diego County was organized in February 1850 as one of California’s original 27 counties, at statehood. It originally stretched east to the Colorado River, covering all of today’s Imperial County and parts of San Bernardino and Riverside counties; those areas split off as Riverside County was created in 1893 and Imperial County in 1907, leaving the county its present boundary. The name traces to San Diego Bay, rechristened in 1602 by the explorer Sebastián Vizcaíno for the Franciscan Saint Didacus — San Diego de Alcalá — whose name his flagship carried. Junípero Serra founded the Presidio and Mission San Diego de Alcalá in 1769, the first permanent Spanish settlement in Alta California. The county today holds 18 federally recognized tribal reservations, more than any county in the United States, reflecting long Kumeyaay, Luiseño and Cupeño presence in the region before Spanish contact.

Getting There

Interstate 5 runs the coast through San Diego, Chula Vista, Encinitas, Carlsbad and Oceanside; Interstate 15 is the inland route through Escondido toward Temecula and Riverside County; Interstate 8 crosses the county east-west from San Diego to the desert and on to Yuma, Arizona. State Routes 78, 94, 52, 56 and the SR-125 toll road fill in cross-county connections.

• Los Angeles — 120 miles north
• Tijuana, Mexico — on the county’s southern border, no mileage to cross
• Phoenix, Arizona — 355 miles east
• Las Vegas, Nevada — 330 miles northeast

San Diego International Airport (SAN), also called Lindbergh Field, is the nation’s busiest single-runway commercial airport and sits inside the city of San Diego. Amtrak’s Pacific Surfliner serves the Santa Fe Depot downtown plus stations in Solana Beach and Oceanside.

Frequently Asked Questions

Where is San Diego County?
It is in the southwest corner of California, bordering the Pacific Ocean to the west and Mexico to the south, about 120 miles south of Los Angeles.

What is the population of San Diego County?
3,298,634 at the 2020 census, an estimated 3,298,799 by 2024 — California’s second-most populous county.

How big is San Diego County?
4,207 square miles (10,899 km2) of land, plus about 319 square miles of water.

What is the county seat of San Diego County?
The city of San Diego, California’s second-most populous city.

How many cities are in San Diego County?
18 incorporated cities, plus at least 37 unincorporated census-designated places and dozens of smaller backcountry communities.

What ZIP codes does San Diego County cover?
Roughly 90 ZIP codes in total, from 92101 in downtown San Diego to 92036 in the mountain town of Julian.

Does San Diego County have Native American reservations?
Yes — 18 federally recognized tribal reservations, more than any other county in the United States.

More counties in this state: Towns and villages in California.