Split Rock (Wyoming)

The mountain summit was listed on the National Register of Historic Places in 1976 for its historic significance.

Geology

Fifty million years ago the Sweetwater River Valley and the Granite Range began to form. The range was created as a segment of the Rocky Mountains. Then, fifteen million years ago the area dropped downward creating a bowl. The erosion of the surrounding highlands, accumulated to 3,000 feet (910 m). As the area continued downward, ‘Moonstone Lake’ formed about ten million years ago. It as large, shallow, and briny, adding an additional 1,500 feet (460 m) of sediments, with some uranium concentrations. The erosion, stripped the surrounding high points, exposing the Granite Range.

The Continental Divide follows the southern rim of the basin, encompassing the Wind River and Sweetwater Valleys, following the crest of the Wind River Range, with the eastward extension including (east to west) the Ferris Mountains, Green Mountains, Crooks Mountain and the Antelope Hills. There are a few breaks in this range of mountains, i.e., Muddy Gap, Crooks Gap and the broad slope called South Pass. This extended valley is a natural ramp built from the sands of ancient Moonstone Lake. The Sweetwater serpentine s through the eastern basin as a clear mountain stream. It has easy slopes, fresh water, and abundant grass. By pack train, wagon or handcart traveled the nineteenth century emigrant, seeking as direct a route as possible through the Great Plains and Rocky Mountains. The Sweetwater segment begins near the Alcova Reservoir, leaving the valley of the North Platte River. After 100 miles (160 km) it exits through South Pass.