San Geronimo Valley is located in Marin County, California, composed of four unincorporated towns: Woodacre, San Geronimo, Forest Knolls, and Lagunitas. It is a fairly close-knit community, with a rather liberal citizenry. The farther west one goes along the valley, the more forested the land becomes. The valley is bisected roughly east-to-west 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. Most of the residents reside on the south, shadier, side of the valley.