Craters of the Moon National Monument and Preserve is a U.S. National Monument and national preserve in the Snake River Plain in central Idaho. It is located along US 20 between the small towns of Arco and Carey. The protected area's features are volcanic and represent one of the best-preserved flood basalt areas in the continental United States. Pioneers traveling in wagon trains on the Oregon Trail in the 1850s and 1860s followed an alternative route in the area that used old Indian trails that skirted the lava flows. This alternative route was later named Goodale's Cutoff and part of it is in the northern part of the monument. Photo by the Bureau of Land Management.