San Geronimo Valley (colloquially known as "The Valley" by citizens of West Marin) is a valley in Marin County, California, composed of four unincorporated towns: Woodacre, San Geronimo, Forest Knolls, and Lagunitas. Residents of San Geronimo Valley and surrounding areas refer to it as "The Valley." It is a fairly close-knit community, with a rather liberal citizenry. The farther west, the more forested the land becomes. The valley is bisected by Sir Francis Drake Boulevard; a number of streets in the towns along this road were constructed on the former right of way of the Northwestern Pacific Railroad. The valley has numerous hiking/biking trails.