The Great Salt Lake lies mainly in which U.S. state? The Great Salt Lake lies mainly in Utah.
The lake occupies a broad basin in northern Utah and is a remnant of prehistoric Lake Bonneville. During the Ice Age, Lake Bonneville covered much of western Utah and extended into small parts of Idaho and Nevada. As the climate warmed, the larger lake shrank, leaving the Great Salt Lake and several smaller remnants.
It is an endorheic, or terminal, lake: rivers flow into it, but there is no outlet to the ocean. Water leaves mainly through evaporation, so minerals accumulate and make the lake hypersaline—often saltier than seawater. That high density makes floating unusually easy.
The Great Salt Lake is not the same as Utah Lake, a separate freshwater lake south of Salt Lake City. Its size changes dramatically with drought, precipitation, water diversions, and evaporation. It also supports brine shrimp and huge populations of migratory birds, making it important far beyond its famous salt content.