Lander, Wyoming in the context of Wind River Indian Reservation

The Great Divide Basin or Great Divide Closed Basin is an area of land in the Red Desert of Wyoming where none of the water falling as rain to the ground drains into any ocean, directly or indirectly. It is thus an endorheic basin, one of several in North America that adjoin the Continental Divide. To the south and west of the basin is the Green River watershed, draining to the Gulf of California/Pacific Ocean; to the north and east is the North Platte watershed, draining to the Gulf of Mexico. The basin is very roughly rectangular in shape; the northwest corner is at Oregon Buttes near South Pass, about 40 miles (64 km) southwest of Lander, and the southeast corner is in the Sierra Madre Range near Bridger Pass, about 20 miles (32 km) southwest of Rawlins.

South Pass (elevation 7,412 ft (2,259 m) and 7,550 ft (2,300 m)) is a route across the Continental Divide, in the Rocky Mountains in southwestern Wyoming. It lies in a broad high region, 35 miles (56 km) wide, between the nearly 14,000 ft (4,300 m) Wind River Range to the north and the over 8,500 ft (2,600 m) Oregon Buttes and arid, saline near-impassable Great Divide Basin to the south. The Pass lies in southwestern Fremont County, approximately 35 miles (56 km) SSW of Lander.

Though it approaches a mile and a half high, South Pass is the lowest point on the Continental Divide between the Central and Southern Rocky Mountains. The passes furnish a natural crossing point of the Rockies. The historic pass became the route for emigrants on the Oregon, California, and Mormon trails to the West during the 19th century. It was designated as a U.S. National Historic Landmark on January 20, 1961.