The low ridge at the south end of this valley forms the south rim of the Great Basin, which in prehistoric times was the bed of a vast body of water now referred to as Lake Bonneville. It was so named in honor of Captain Benjamin L. E. Bonneville, who in 1833 directed the first scientific exploration of its largest remnant—Great Salt Lake.
Lake Bonneville extended 350 miles to the north and was in places 145 miles wide, with a maximum depth of 1050 ft. Its shoreline is clearly discernible on the mountain slopes fringing the basin. Through the Red Rock Pass in what is now southern Idaho, the lake drained into the Pacific Ocean, its waters flowing down the Portneuf, Snake, and Columbia Rivers.
Of this large body of water, the Great Salt Lake, Utah, Sevier, and other small lakes remain. Lying in the lowest part of the lake bed and having no outlet, Great Salt Lake has become the "Dead Sea" of the Western Hemisphere.