Which US national park has the world's largest gypsum dune field?

White Sands National Park in New Mexico contains the world’s largest gypsum dune field. Its brilliant white dunes cover part of the Tularosa Basin, where wind has shaped sand-sized grains of gypsum into constantly shifting hills and ridges.

The dunes began with gypsum deposited by ancient seas and later uplifted into the surrounding mountains. Rain and snowmelt dissolved the mineral and carried it into the closed Tularosa Basin. As ancient Lake Otero and later shallow pools evaporated, they left behind selenite crystals. Wind and weather gradually broke those crystals into the soft gypsum sand seen today.

The area was protected as White Sands National Monument in 1933 and redesignated a national park in 2019. The park protects roughly 42% of the broader dunefield, while the remainder lies within the adjacent White Sands Missile Range. Visitors often compare it with Great Sand Dunes National Park, but those Colorado dunes are made of ordinary mineral sand, whereas White Sands is famous for gypsum.