Great Sand Dunes National Park and Preserve is a United States National Park located in the San Luis Valley, in the easternmost parts of Alamosa County and Saguache County, Colorado, United States. Originally created as Great Sand Dunes National Monument on March 17, 1932, Great Sand Dunes National Park and Preserve was established by an act of the United States Congress on September 13, 2004. The park includes 107,342 acres, and the preserve protects an additional 41,686 acres.The park contains the tallest sand dunes in North America, rising to a maximum height of 750 feet from the floor of the San Luis Valley on the western base of the Sangre de Cristo Range. The dunes cover an area of about 30 sq mi and are estimated to contain over 5 billion cubic meters of sand.