The dunes at Bruneau Dunes State Park are unique in the Western Hemisphere. Others in the Americas form at the edges of natural basins; these form near the center. They include the largest single-structured sand dune in North America, with a peak 470 feet above the lakes.

The combination of 1) a source of sand; 2) a relatively constant wind activity; and 3) a natural trap have caused sand to collect in this semicircular basin for about 12,000 years. Unlike most dunes, these do not drift far. The prevailing winds blow from the southeast 28 percent of the time and from the northwest 32 percent of the time, keeping the dunes fairly stable. The two prominent dunes cover about 600 acres.