Great Sand Dunes National Park and Preserve
Great Sand Dunes National Park and Preserve, 132.4 sq mi (343 sq km), in the San Luis Valley of S Colorado; est. as a national monument 1932, designated a national park 2004. Lying in an area of high desert between the San Juan and Sangre de Cristo mtns., the park's sand dunes are the tallest in North America, extending up to 750 ft (230 m). They were formed when sand and gravel deposits left by ancient streams flowing into the valley were blown toward the Sangre de Cristos after the streams dried up. The intermittent Medano Creek is located within the park. The mountainous preserve includes pinyon pines and aspens, spruce and fur forests, alpine lakes, and tundra. See National Parks and Monuments (table).