Endangered San Bruno elfin butterflies are only found on the San Francisco Peninsula, on a handful of undeveloped steep, rocky hillsides where their caterpillars’ host plant, broadleaf stonecrop, still thrives. Milagra Ridge in Golden Gate National Recreation Area is one such spot. The Golden Gate National Parks Conservancy’s Park Stewardship Program has been keeping tabs on San Bruno elfins at Milagra Ridge since 1999.