| Tomales Bay | |
|---|---|
Tomales Bay as viewed from Tomales Point Trail | |
| Coordinates | 38°08′55″N122°53′52″W / 38.14860°N 122.89787°W /38.14860; -122.89787 |
| Type | Bay |
| Ocean/sea sources | Pacific Ocean |
| Basin countries | United States |
| Max. length | 15 km (9.3 mi) |
| Max. width | 1.6 km (0.99 mi) |
| Settlements | Inverness Inverness Park Point Reyes Station Marshall |
| Official name | Tomales Bay |
| Designated | October 21, 2002 |
| Reference no. | 1215[1] |
Tomales Bay is a long, narrowinlet of thePacific Ocean inMarin County in northernCalifornia in theUnited States.


Tomales Bay is approximately 15 mi (24 km) long and averages nearly 1.0 mi (1.6 km) wide, with relatively shallow depths averaging 18 ft,[2] effectively separating thePoint Reyes Peninsula from the mainland of Marin County. It is located approximately 30 mi (48 km) northwest ofSan Francisco. The bay forms the eastern boundary ofPoint Reyes National Seashore. Tomales Bay is recognized for protection by theCalifornia Bays and Estuaries Policy.[3] On its northern end, it opens out ontoBodega Bay, which shelters it from the direct currents of the Pacific (especially theCalifornia Current). The bay is formed along a submerged portion of theSan Andreas Fault. The fault divides thePoint Reyes Peninsula through Tomales Bay in the north, and theBolinas Lagoon in the south. The Bear Valley Visitor Center in Point Reyes Station is home to the Earthquake Trail, where visitors can see a visible rift formed on the fault during the 1906 San Francisco earthquake.[4]
Towns bordering Tomales Bay includeInverness,Tomales,Inverness Park,Point Reyes Station, andMarshall. Additional hamlets includeNick's Cove, Spengers, Duck Cove, Shallow Beach, and Vilicichs.Dillon Beach lies just to the north of the mouth of the bay, andTomales just to the east.[5]
California State Parks department monitored, surf-free beaches on the bay include Heart's Desire, Shell Beach, Indian Beach, Pebble Beach, and Millerton Point. Most beaches require a hike-in, so if visiting, prepare with walkable shoes. Swimming, picnicking, sailing, kayaking, motorboating, and fishing are all popular activities on the bay.[6]
Watercrafts may be launched on Tomales Bay from the public boat ramp at Nick's Cove, north of Marshall. Thesandbar at the mouth of Tomales Bay is notoriously dangerous, with a long history of small-boat accidents.[7]

Oyster farming is a major industry on the bay. The two largest producers are Hog Island Oyster Company andTomales Bay Oyster Company, both of which retail oysters to the public and have picnic grounds on the east shore. Hillsides east of Tomales Bay are grazed by cows belonging to local dairies. There is also grazing land west of the bay, on farms and ranches leased from Point Reyes National Seashore.
TheCalifornia Office of Environmental Health Hazard Assessment (OEHHA) has developed a safe eating advisory for fish caught here, based on levels of mercury orPCBs found in local species.[8]
The bay is home to many aquatic species, and its habitat diversity is supported byeelgrass beds and intertidal mudflats. In the bay’s waters, bony and cartilaginous fish species includinghalibut,coho salmon,bat rays andleopard sharks[9] can be found.[10] Along muddy parts of bay's shore, it is common to find the gastropods such as the invasiveFalse Cerith snail, recognizable from its dextrally coiled shape and brown-gray pattern.[11]
The area surrounding Tomales Bay was once the territory of theCoast Miwok tribe. Documented villages in the area includedEcha-kolum (south ofMarshall),Sakloki (oppositeTomales Point),Shotommo-wi (near the mouth of theEstero de San Antonio), andUtumia (near Tomales).[12] The tribe's history is deeply rooted in the bay and its surrounding areas. Fishing and hunting supported their livelihood, and shells and clams collected from the bay's shore served as currency.[13]
Francis Drake is thought to have landed in nearby Drakes Estero in 1579.[14] Members of theVizcaíno Expedition found the Bay in 1603, and thinking it a river, named itRio Grande de San Sebastian.[15]
Early 19th-century settlements constituted the southernmost Russian colony in North America and were spread over an area stretching fromPoint Arena to Tomales Bay.[16]
Thenarrow gaugeNorth Pacific Coast Railroad fromSausalito was constructed along the east side of the bay in 1874 and extended to theRussian River until it was dismantled in 1930.[17]
Tomales Bay State Park was formed to preserve some of the bay shore; it opened to the public in 1952.[14]
TheRamsar Convention, signed in 1971, listed Tomales Bay as awetland of international importance.
The Giacomini Wetland Restoration Project, completed in 2008, returned to wetland several hundred acres at the south end of the bay that had been drained for grazing in the 1940s.

The Marconi State Historical Park (formerly Marconi Conference Center State Historic Park) preserves a small hotel built in 1913 byGuglielmo Marconi to house personnel who staffed his transpacific radio station nearby.RCA purchased the station from Marconi in 1920, and it closed in 1939, though other nearby radio stations on the Point Reyes Peninsula still operate today. It was purchased and used by the controversialnew religious movementSynanon in 1964, and given to the state in 1984 to operate as a conference center.[18]