The trail follows the river upstream to Fort Laramie, a prominent military and trading post in the region.
The southern route also follows the river along the edge of the Laramie Mountains to an area near the current towns of Casper and Glenrock.
Famous landmarks along the southern route included Ayres Natural Bridge and Register Cliff, one of a number of locations along the trail in Wyoming where settlers carved their names.
Later settlers who had crossed to the northern side of the river at Casper would come to favor a route through a small valley called Emigrant Gap which headed directly to Rock Avenue, bypassing Red Buttes.
The trail crosses the Sweetwater three more times and encounters a large hill known as Rocky Ridge on the northern side of the river.
[10] Crossing South Pass meant that the settlers had truly arrived in the Oregon Territory, though their ultimate destination was still a great distance away.
South of the Dry Sandy ford, the trail split into two major sections, the main route which continues south to Fort Bridger, and the Sublette Cutoff, which proceeds west directly to the Green River and Bear River valleys, bypassing Fort Bridger.
Here, a secondary path to the Sublette Cutoff leads from the Little Sandy Pony Express station that was based here during the emigration period.
The Mormon Trail continues southwest, fording the Bear River and crossing into Utah south of the current town of Evanston.
The Sublette-Greenwood Cutoff was opened in 1844 by the Stephens-Townsend-Murphy Party led by mountain men Caleb Greenwood and Isaac Hitchcock.
A traveler in 1846 wrote: We lay by preparing to Crossing the Cut off to Green river a distance of 40 miles without Wood or Water set out on the Journey at 3AM and landed on Green river the distance aforesaid at 3'Oclock of the 19th it being 24 hours drive[18] The route reached the height of popularity during the California Gold Rush of the 1850s when a desire to speed to the California gold fields outweighed the risks.
The popularity of the guide book during the 1850s cemented the name, though most scholars today call it the Sublette-Greenwood Cutoff after its original discoverer.
[19] As on the main route, several ferries operated where the cutoff crossed the Green River near the present day town of La Barge.
West of the ford is its namesake, Names Hill, which is a prominent emigrant "recording area" with signatures and other carvings.
Expeditions under the command of Frederick W. Lander surveyed a new route starting at Burnt Ranch following the last crossing of the Sweetwater River before it turned west over South Pass.
The trail entered Star Valley about six miles (10 km) south of the present town of Smoot, Wyoming.
From Smoot, the road then continued north about 20 miles (32 km) down Star Valley west of the Salt River before turning almost due west at Stump Creek near the present town of Auburn, Wyoming, and passing into the present state of Idaho and following the Stump Creek valley about 10 miles (16 km) northwest over the Caribou Mountains (this section of the trail is now accessible only by US Forest Service path as the main road (Wyoming Highway 34) now goes through Tincup canyon to get across the Caribous.)
After crossing the Caribou Range the road split, turning almost 90 degrees and progressing southwest to Soda Springs, Idaho, or alternately heading almost due west and passing south of Grays Lake (now part of the Grays Lake National Wildlife Refuge[23]) to Fort Hall.
The Lander Road had good grass, fishing, water and wood but was high, rough and steep in many places.
By crossing the lush Wyoming and Salt River Ranges instead of circling via the deserts to the south, the route provided ample wood, grass and water for the travelers, and cut nearly seven days off the total travel time for wagon trains going to Fort Hall.
Funds were appropriated in 1858 and 115 men (hired in Utah) completed the road in Wyoming and Idaho in 90 days, clearing timber and moving about 62,000 cubic yards (47,000 m3) of earth.