National monument, south-central New Mexico, U.S. Established in 1933, it covers 225 sq mi (583 sq km) and lies between the San Andres and the Sacramento mountains.
Its white gypsum sand constantly drifts into dunes 10–60 ft (3–18 m) high. The San Andres National Wildlife Refuge, White Sands Missile Range, and Holloman Air Force Base are nearby.