Blood, Trauma, and Biohazard Cleanup in San Geronimo, CA

San Geronimo is an unincorporated census-designated place in Marin County, one of the four small towns of the San Geronimo Valley alongside Woodacre, Forest Knolls, and Lagunitas, located about 8 miles southwest of downtown Novato at an elevation of 292 feet.

Its name is Spanish for "St. Jerome," and the valley takes its name from the Mexican-era Rancho San Geronimo.

Before 1877 the place was called Nicasio, and its post office opened in 1895, closed in 1910, and re-opened in 1911.

Adolph Mailliard and Ann Eliza Ward bought Rancho San Geronimo in 1868 and bred thoroughbred racehorses there, including the famous stallion Monday, who sired most of the race horses in California; their son Joseph Mailliard grew up on the ranch and became a noted ornithologist.

San Geronimo had a population of 510 at the 2020 census, up from 446 in 2010 and 436 in 2000, the first census in which it appeared as a census-designated place.

San Geronimo has 198 households averaging about 2.6 people each, and about 68% of its occupied homes are owner-occupied.

The community's former San Geronimo Golf Course, a 157-acre site, was purchased by The Trust for Public Land in 2018 and opened to the public as a park while habitat restoration and planning for its future use continue.

Local students are served by the Lagunitas Elementary School District and the Tamalpais Union High School District.