Anderson Marsh State Historic Park, Nature reserve and historic site at Clear Lake, California.

Anderson Marsh State Historic Park is a nature reserve on the southeastern shore of Clear Lake featuring tule marshes, oak woodlands, grasslands, and wetland areas. The park includes multiple ecosystems with trails that pass through different habitat types.

Anderson Marsh holds archaeological sites of the Southeastern Pomo, some dated at over 10,000 years old; John Parker recorded 43 prehistoric sites and nominated the area to the National Register of Historic Places. John Grigsby homesteaded here in 1854 and built a small house. In 1884 Scotsman John Still Anderson bought the property, built the Ranch House, and ran a dairy and beef cattle operation; his descendants lived in the house until the 1960s.

The old ranch buildings show how settlers lived and worked the land in the 1800s. These structures tell the story of how European settlers shaped the region and its uses.

The park is open from sunrise to sunset with multiple hiking trails through different ecosystems. Early morning and late afternoon hours are best for bird watching when animals are most active.

Some of the archaeological sites recorded here are among the oldest found in California, dated at over 10,000 years old. John Parker documented 43 prehistoric sites and nominated the area to the National Register of Historic Places, starting the campaign that led to its acquisition as a state park.