Bruneau Dunes State Park is home to the tallest freestanding sand dunes in North America, with the highest reaching 470 feet. The dunes at Bruneau Dunes State Park are unique in the Western Hemisphere. Other dunes in the Americas form at the edge of a natural basin while the Bruneau dunes form near the center. The basin has acted as a natural trap for over 12,000 years. The dunes may have started with sands from the Bonneville Flood which occurred about 15,000 years ago. 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. Unlike most dunes, the sands here do not drift far.