Marin County, California

Marin is a county in California, United States, directly north of San Francisco across the Golden Gate Bridge. It had a population of 262,321 at the 2020 census, an estimated 257,969 by 2024, and covers 520 square miles (1,347 km2) of land centred near 38°02′N 122°44′W. Another 308 square miles of San Francisco and San Pablo Bay waters fall inside the county line.

San Rafael is the county seat and the county’s largest city; its postal code is 94901. Marin holds 6 cities, 5 incorporated towns and more than a dozen unincorporated communities and census-designated places, and it runs on Pacific time. Its FIPS code is 06041.

Towns & Villages in Marin County

Marin has 11 incorporated municipalities — 6 cities and 5 towns, none larger than San Rafael — plus 14 census-designated places (CDPs) covering everything from the Tiburon Peninsula to the Point Reyes coast. The table below marks incorporated cities and towns as City or Town, and unincorporated CDPs as CDP.

A few pairs get mixed up. Belvedere and Tiburon are separate cities on the same peninsula and share the 94920 ZIP, which leads outsiders to treat them as one place. Strawberry is unincorporated land wedged against Mill Valley, uses Mill Valley’s 94941 ZIP, and has no city government of its own despite the local shopping center bearing its name. San Quentin the community is a small residential pocket next to San Quentin Rehabilitation Center — the prison and the village share a name but not a government.

ZIP Codes

• 94901 — San Rafael (also serves the Canal and Peacock Gap neighborhoods)
• 94903 — San Rafael post office, covering Lucas Valley–Marinwood
• 94904 — Greenbrae, also covering Kentfield
• 94920 — Tiburon, also covering Belvedere
• 94924 — Bolinas
• 94925 — Corte Madera
• 94929 — Dillon Beach
• 94930 — Fairfax
• 94937 — Inverness
• 94939 — Larkspur
• 94941 — Mill Valley, also covering Tamalpais-Homestead Valley and Strawberry
• 94945 — Novato
• 94946 — Nicasio
• 94956 — Point Reyes Station
• 94957 — Ross
• 94960 — San Anselmo, also covering Sleepy Hollow
• 94964 — San Quentin
• 94965 — Sausalito, also covering Marin City and Muir Beach
• 94970 — Stinson Beach
• 94973 — Woodacre

Small hamlets in the San Geronimo Valley — Forest Knolls and Lagunitas among them — route through neighboring post offices rather than carrying a ZIP of their own, a legacy of a valley too sparsely settled for its own postal branch.

Geography

Marin occupies the tip of a peninsula between San Pablo Bay and the Pacific Ocean, so water bounds it on three sides. The terrain runs from the tidal marshes and inlets of the eastern bayshore, through the redwood-forested slopes of Mount Tamalpais in the center, to the exposed Point Reyes headland on the west — itself nearly a separate landmass, split from the mainland by the San Andreas Fault running through Tomales Bay and the Olema Valley. Muir Woods National Monument and the Marin Headlands, part of the Golden Gate National Recreation Area, sit in the county’s south; Point Reyes National Seashore covers most of the western coast.

Sonoma County borders Marin to the north, the only county Marin touches by land. San Francisco lies directly south across the Golden Gate Strait, reached by the Golden Gate Bridge rather than any road connection over land. Contra Costa County sits across San Pablo Bay to the east, linked by the Richmond–San Rafael Bridge. More detail on the county across the northern line: Sonoma County.

Demographics

Marin counted 262,321 residents at the 2020 census, with an estimated 257,969 by 2024 — a slight decline typical of high-cost Bay Area counties over that period. San Rafael and Novato are the two largest communities, together holding more than 40 percent of the county’s population. Median household income reached $149,091 in 2024, one of the highest county figures in California. Median age is 47.4, well above the statewide median, reflecting a county with fewer young families than it had a generation ago. Population density across the 520 square miles of land works out to roughly 495 people per square mile, concentrated along the US-101 corridor from San Rafael to Novato.

Economy & Local Life

Marin’s economy employs about 126,000 people. Professional, scientific and technical services is the largest sector at 22,751 workers, followed by health care and social assistance at 16,074 and retail trade at 11,738. BioMarin Pharmaceutical, headquartered in Novato, is one of the county’s largest private employers; MarinHealth Medical Center in Greenbrae and Kaiser Permanente’s San Rafael campus anchor health care. Lucasfilm’s Skywalker Ranch, tucked in a Nicasio valley west of Lucas Valley, has drawn film and sound production work to the county since the 1980s. Dominican University of California and College of Marin serve as the county’s two main higher-education campuses, both based in and around San Rafael. The Marin County Fair, held over the Fourth of July weekend at the Marin Civic Center, is the county’s largest annual gathering.

History

Coast Miwok people lived across what is now Marin for thousands of years before Spanish missionaries arrived. Mission San Rafael Arcángel, founded in 1817 as a hospital outpost for sick Ohlone and Miwok converts from Mission Dolores in San Francisco, became the county seat’s namesake and the northernmost of California’s 21 missions. The county itself was organized on February 18, 1850, as one of California’s original 27 counties, and takes its name from a Coast Miwok leader most accounts call Chief Marin, who led resistance against Mexican forces in the 1810s before later working at the mission.

San Quentin’s state prison opened its first cellblock in 1854, making it California’s oldest; it was renamed San Quentin Rehabilitation Center in 2023 under a state initiative shifting its focus toward education and reentry programs. During World War II, the Marinship shipyard in Sausalito built Liberty ships and tankers, drawing tens of thousands of workers to the county in a few years and reshaping Sausalito and Marin City, which was built as wartime worker housing.

Getting There

US-101 runs the length of the county north to south, crossing the Golden Gate Bridge into San Francisco at the southern end. State Route 1 follows the coast from the Marin Headlands to Point Reyes and on to Sonoma County. I-580 enters the county over the Richmond–San Rafael Bridge and ends at US-101 in San Rafael — the only stretch of interstate highway in Marin.

• San Francisco — 12 miles south
• Oakland — 20 miles east via the Richmond–San Rafael Bridge
• Santa Rosa — 30 miles north
• Sacramento — 90 miles northeast

San Francisco International Airport, about 25 miles south, is the nearest major commercial airport. The Sonoma–Marin Area Rail Transit (SMART) line runs passenger trains through San Rafael and Novato north to Santa Rosa; the nearest Amtrak connection is the Richmond station across the bay, reached by Amtrak Thruway motorcoach.

Frequently Asked Questions

Where is Marin County?
Marin County is in California, United States, on the peninsula directly north of San Francisco across the Golden Gate Bridge.

What is the population of Marin County?
It had a population of 262,321 at the 2020 census, with an estimated 257,969 residents by 2024.

How big is Marin County?
Marin covers 520 square miles (1,347 km2) of land, plus another 308 square miles of bay and ocean water.

What is the county seat of Marin County?
San Rafael is the county seat and the county’s largest city.

How many towns and cities are in Marin County?
Marin has 11 incorporated municipalities — 6 cities and 5 towns — plus 14 census-designated places and several smaller unincorporated communities.

What ZIP codes serve Marin County?
ZIP codes range from 94901 in San Rafael to 94973 in Woodacre, with most incorporated cities and towns holding their own code and smaller CDPs sharing a neighbor’s.

Does Marin County have any interstate highways?
Only one stretch: I-580 crosses the Richmond–San Rafael Bridge from Contra Costa County and ends at US-101 in San Rafael. US-101 itself is a US highway, not an interstate, for its full run through the county.

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