Triangle Marsh, on San Francisco Bay at the base of Ring Mountain on the Tiburon Peninsula, is both a wetland and an archaeological site. Petroglyphs and other finds on Ring Mountain provide significant evidence of Native American habitation in the area and likely show that early Miwok peoples used the marsh’s marine resources. This connection ties the tidal marsh to both the bay’s natural history and long-term Indigenous use of shoreline habitats. Covering 31 acres, the site has also gained ecological importance as restored upland and wetland habitat and as refuge for federally endangered species including the clapper rail and salt marsh harvest mouse.