Great Salt Plains Lake, Reservoir in Alfalfa County, Oklahoma, United States

Great Salt Plains Lake is a reservoir in Alfalfa County, Oklahoma, with extensive shorelines and saline water throughout. The body of water features shallow areas and coves that support a range of recreational and wildlife observation opportunities.

A 1931 study for the U.S. Army Corps of Engineers proposed a flood-control dam at the Great Salt Plains; Congress authorized it in 1936, design began in 1937, and construction started in September 1938. The dam was completed in July 1941, creating a reservoir with a capacity of 31,420 acre-feet.

The lake forms part of the Salt Plains National Wildlife Refuge, where numerous bird species gather at Ralstin Island for nesting and breeding activities.

Great Salt Plains State Park, on the lake's shore, has boat ramps, a fishing dock, a swimming beach, picnic sites and equestrian trails. Campers can use RV and tent sites, cabins and comfort stations with showers. The average depth is only 4 feet, so the water is shallow throughout.

On the lake's west edge, visitors can dig for selenite crystals that contain an hourglass inclusion found only at the Great Salt Plains. The salt was laid down by repeated rises of a shallow sea millions of years ago and is held in place by saline groundwater a few feet below the surface; evaporation leaves a salt layer and forms the crystals.