Great Sand Dunes National Park and Preserve conserves an area of large sand dunes up to 750 feet tall on the eastern edge of the San Luis Valley, and an adjacent national preserve in the Sangre de Cristo Range, in south-central Colorado. The park was originally designated Great Sand Dunes National Monument on March 17, 1932, by President Herbert Hoover. The original boundaries protected an area of 35,528 acres. A boundary change and re-designation as a national park and preserve was authorized on November 22, 2000, and then established by an act of Congress on September 24, 2004. The park encompasses 107,342 acres while the preserve protects an additional 41,686 acres for a total of 149,028 acres.
The park contains the tallest sand dunes in North America. Visitors must walk across the wide and shallow Medano Creek to reach the dunes in spring and summer. The creek typically has a peak flow from late May to early June. From July to April, it is usually no more than a few inches deep, if there is any water at all. Hiking is permitted throughout the dunes with the warning that the sand surface temperature may reach 150 °F in summer. You may start up the dunes in the morning barefoot when it is quite cool but when the sun starts heating up the sand it is impossible to walk. The old chestnut about taking three steps forward and two steps back also definitely applies to hiking up these dunes.
Going down the sand dunes can be much quicker!