The hills are bordered to the north by the Santa Rosa Plain and Laguna de Santa Rosa; to the east by the San Pablo Bay, the northern arm of San Francisco Bay; to the south by the Golden Gate Strait; and to the west by the San Andreas Fault, running through Tomales Bay, Olema Valley, Bolinas Lagoon, and Stinson Beach.

Parts of the hills are protected for their scenic beauty by Mount Tamalpais State Park and the Golden Gate National Recreation Area.

The many ridges and peaks of these hills form a dramatic backdrop to the Golden Gate Bridge, the San Francisco skyline, and several towns around Richardson Bay when viewed from the south.

[1] Since these hills lie near the Pacific Ocean, they force much of the incoming moisture out of the air and rainfall here is much greater than the bayside of Marin County.

The low hills to the east support only California oak woodlands, chaparral and grasslands.