The GLBT Historical Society Museum at 4127 18th Street, a few steps off Castro, opened in 2011 as the first standalone museum of LGBTQ history in the United States. It is run by the GLBT Historical Society, founded in 1985, which holds one of the largest archives of queer history in the world.
Exhibitions draw on that archive: Harvey Milk’s personal effects, protest materials, oral histories, photographs, and artifacts spanning more than a century of San Francisco’s queer life. The museum is small, admission is low-cost, and it is closed some weekdays. Check hours before visiting.