Devils Postpile National Monument in eastern California protects a compact but distinctive Sierra Nevada landscape centered on two features of the Middle Fork San Joaquin River valley: the Devils Postpile basalt formation and Rainbow Falls. Formed by a lava flow less than 100,000 years ago, the dark cliff cooled into unusually regular columns, later exposed and polished by glaciation. The area narrowly escaped destruction by a proposed hydroelectric project after being left outside Yosemite following a 1905 boundary change tied to nearby gold discoveries. With support from John Muir and other Californians, the federal government preserved it instead, and President William Howard Taft established the monument in 1911.