The Duxbury Reef Area of Special Biological Significance (ASBS) in Marin County has 3.4 miles of coastline. This ASBS lies entirely within the Gulf of the Farallones National Marine Sanctuary. It includes Duxbury Reef State Marine Conservation Area and Extension, which is managed by the California Department of Fish and Game.

The ASBS is bordered by many different land uses. The northern, less-populated half has only two permanent residences, a six-man Coast Guard Station, and a cancer hospice. Livestock grazing occasionally takes place in this area, and a few trails lead to an expansive beach. The road gets limited automobile traffic. The town of Bolinas is to the south.

Key pollution threats are urban and stormwater runoff.

The area is extremely popular with surfers, swimmers and fishermen.

ASBS Area: 875 acres

County: Marin

Regional Board Area: San Francisco Bay RWQCB

Year designated: 1974 (Resolution 74-28)

ASBS Index No.: 11