What valley in the US is the remains of an evaporated salt lake?
The Great Salt Lake Desert in Utah is what remains of a salt lake.
The Great Salt Lake is the largest natural lake west of the Mississippi River. It is all that remains of a prehistoric inland sea. The Great Salt Lake has no natural drainage, and as the water evaporates, the salt remains. As result, the Great Salt Lake is more than seven times salter than the oceans. People can easily float in the dense water.
Echo Canyon was the main route into the Salt Lake Valley. This is the route that the Mormons expected the army to take to come into the Salt Lake Valley. The army attempted to go around the Wasatch Mountains and come down into the Salt Lake Valley from Idaho via Soda Springs, but after several days of slow and exhaustive traveling that expedition turned around (Oct. 1857).