Solano County, California

Solano County is a county in California, United States, about 35 miles northeast of San
Francisco. It had a population of 453,491 at the 2020 census, an estimated 455,376 by 2025, and
covers 906 square miles (2,350 km2) centred near 38°16′N 121°56′W.

Fairfield is the county seat; its postal code is 94533. The county holds 7 incorporated cities
and 13 unincorporated communities, and it runs on Pacific Time. Its FIPS code is 06095.

Towns & Villages in Solano County

Solano County has 20 named places on record: 7 incorporated cities and 13 unincorporated
communities, six of which carry formal census designated place (CDP) status. CDP stands for
census designated place; Unincorp. covers crossroads and rural hamlets with no current population
count of their own.

Birds Landing’s post office closed in 2001, so its last documented count is a 2000-census
figure of 130 residents rather than a current one; the ZIP survives for rural-route mail. Batavia,
Denverton, Maine Prairie, Mankas Corner and Tremont Township are historic rail or stagecoach
crossroads with no formal census tract of their own and no current population figure on record.

ZIP Codes

• 94533 — Fairfield (also serves 94534 and the Travis Air Force Base ZIP, 94535)
• 94590 — Vallejo (also serves 94589, 94591 and 94592)
• 95687 — Vacaville (also serves 95688 and 95696)
• 94534 — Green Valley, Rockville and Cordelia, all delivered under the Fairfield-area code
• 94585 — Suisun City (also serves Collinsville)
• 94510 — Benicia
• 95620 — Dixon
• 94571 — Rio Vista
• 95625 — Elmira
• 94512 — Birds Landing

Hartley, Allendale, Batavia, Denverton, Maine Prairie, Mankas Corner and Tremont Township have
no ZIP code of their own; mail there is delivered under the nearest incorporated city’s
code.

Geography

Solano County sits at the northeastern edge of the San Francisco Bay Area, where the Coast
Ranges give way to the flat farmland of the Sacramento Valley. Of its 906 square miles, 810 are
land and 96 are water, a water share of roughly 11 percent, high for an inland California county.
Suisun Marsh, the largest contiguous estuarine marsh remaining on the west coast of North America,
covers much of the county’s southeast, and the Sacramento River forms part of the boundary
with Contra Costa County before emptying into Suisun Bay near Collinsville. The Montezuma Hills, a
rolling upland in the southeast corner, host one of California’s oldest wind-energy resource
areas.

Napa County lies to the west, Yolo County to the north, Sacramento County to the northeast, and
Contra Costa County to the south across the Carquinez Strait; Sonoma County touches the
county’s northwest corner for a short stretch. Napa County, Yolo County, Sacramento County, Contra Costa County and Sonoma County all border Solano.

Demographics

Solano County had a population of 453,491 at the 2020 census, and the latest estimate puts the
county near 455,376 residents. Vallejo and Fairfield are the two largest communities, together
holding well over half the county’s population. Median household income runs $100,401,
higher than California’s statewide figure of $95,521. Population density works out to
roughly 560 people per square mile of land, moderate for a Bay Area county and concentrated
heavily in the I-80 corridor cities.

Economy & Local Life

Health care and social assistance employs the most workers in the county, about 32,877 people,
followed by retail trade at 23,689 and manufacturing at 17,769. Travis Air Force Base, three miles
east of downtown Fairfield, is the county’s single largest employer with more than 13,000
active-duty, reserve and civilian personnel. Vacaville hosts a cluster of biotechnology and
pharmaceutical plants, including facilities run by Lonza and Kaiser Permanente, on the site once
occupied by Genentech’s original manufacturing campus. Benicia is home to the Valero Benicia
Refinery, one of the largest oil refineries on the West Coast, and Fairfield manufactures Jelly
Belly jelly beans at a factory that also runs public tours. The Suisun Valley American
Viticulture Area, around Mankas Corner, grows wine grapes and olives on land once used for wheat
and quicksilver ore transport. The county’s biggest annual event is the Solano County Fair,
held each June at the Fairgrounds in Vallejo.

History

The California legislature created Solano County on 18 February 1850, one of the state’s
original 27 counties. It was named for Chief Solano, a Suisun leader baptized Francisco Solano who
allied with General Mariano Vallejo in the 1830s. The county seat moved twice before settling
permanently: Benicia held the title first, then Vallejo, before Fairfield became the seat in
1858.

Vallejo briefly served as California’s state capital from 1852 to 1853, and Benicia held
the capital from 1853 to 1854, before the government moved on to Sacramento for good. The restored
Benicia capitol building, built in 1852, is the only surviving structure from any of
California’s pre-Sacramento capitals and is now a state historic park.

Getting There

Interstate 80 crosses the county through Vallejo, Fairfield and Vacaville, linking the region to
San Francisco and Sacramento. Interstate 680 runs south from Benicia across the Carquinez Strait,
and Interstate 505 clips the county’s northwest corner near Allendale. California state
routes 12, 29, 37 and 113 also cross the county.

• San Francisco — about 35 miles southwest
• Sacramento — about 45 miles northeast
• Oakland — about 30 miles south
• Napa — about 15 miles west

Sacramento International Airport and San Francisco International Airport are both roughly 40
miles from Fairfield and share most of the county’s commercial air traffic. Nut Tree Airport
in Vacaville handles general aviation. Amtrak’s Capitol Corridor trains stop at the
Fairfield–Vacaville Station on Vanden Road, connecting to Sacramento, Oakland and San Jose.

Frequently Asked Questions

Where is Solano County located?
It sits in the northeastern San Francisco Bay Area, about 35 miles northeast of San Francisco,
bordered by Napa, Yolo, Sacramento, Contra Costa and Sonoma counties.

What is the population of Solano County?
453,491 at the 2020 census, with a 2025 estimate near 455,376.

How big is Solano County?
906 square miles (2,350 km2), of which 810 square miles are land.

What is the county seat of Solano County?
Fairfield, the county seat since 1858, following earlier stints for Benicia and Vallejo.

How many towns and cities are in Solano County?
Seven incorporated cities — Fairfield, Vallejo, Vacaville, Suisun City, Benicia, Dixon and
Rio Vista — plus 13 unincorporated communities, including the census-designated places
Hartley, Green Valley, Allendale, Rockville, Elmira and Cordelia.

What ZIP codes does Solano County use?
94533, 94534 and 94535 for Fairfield and its CDPs; 94589 through 94592 for Vallejo; 95687, 95688
and 95696 for Vacaville; 94585 for Suisun City; 94510 for Benicia; 95620 for Dixon; 94571 for Rio
Vista; and 95625 for Elmira.

What is Solano County known for?
Travis Air Force Base, the Valero Benicia Refinery, Suisun Marsh, and briefly hosting
California’s state capital at both Vallejo and Benicia in the early 1850s.

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