Santa Fe Dam, California

The Santa Fe Dam is a large flood control structure serving a drainage area of 236 square miles. The dam is meant to hold back mud and debris flows that sometimes descend from the nearby San Gabriel Mountains (which have wiped out communities in the past). The dam and the sacrificial debris retention basin behind it are part of a network of similar structures which include some of the largest dams in the nation. Built by the Army Corps of Engineers in the 1940s, the Santa Fe Dam is over four miles long.