C.A. Thayer is a schooner built in 1895 near Eureka, California. The schooner has been preserved and open to the public at the San Francisco Maritime National Historical Park since 1963. She is one of the last survivors of the sailing schooners in the West coast lumber trade to San Francisco from Washington, Oregon, and Northern California. She was designated a National Historic Landmark on 13 November 1966.

The San Francisco Maritime National Historical Park is located in San Francisco, California, United States. The park includes a fleet of historic vessels, a visitor center, a maritime museum, and a library/research facility. Formerly referred to as the San Francisco Maritime Museum, the collections were acquired by the National Park Service in 1978. The San Francisco Maritime National Historical Park was authorized in 1988; the maritime museum is among the park's many cultural resources. The park also incorporates the Aquatic Park Historic District, bounded by Van Ness Avenue, Polk Street, and Hyde Street.