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 the United States 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/Atlantic Ocean. The basin is very roughly rectangular in shape; the northwest corner is at Oregon Buttes near South Pass, about southwest of Lander, and the southeast corner is in the Sierra Madre Range near Bridger Pass, about southwest of Rawlins. History Although the Great Divide Basin provides a relatively low and easy crossing of the Continental Divide, its aridity and endorheic nature were an obstacle to pioneers during the westward expansion of the United States; it was known as the Saline Plain around the 1870s. Consequently, the Oregon Trail detoured north over South Pass, and the Overland Trail detoured south over Bridger Pass. In contrast, during the construction of the first transcontinental railroad, the Union Pacific was laid directly across the southern part of the basin. (The original railroad map labelled one point along this route as Bridgers Pass, giving rise to the still-common misconception that the railroad followed the Overland Trail.) Roughly the same route across the basin was later taken by the transcontinental highways traversing the region, namely the Lincoln Highway, U.S. 30, and Interstate 80. The basin is also traversed in a north-south direction by U.S. 287 and Wyoming 789. Even today the basin is very sparsely populated, the only incorporated town being Wamsutter, with a population of 451 at the 2010 census. A westward traveler on Interstate 80 crosses from the Gulf of Mexico drainage to the Great Divide Basin at about , roughly 7 miles west of Rawlins. A highway sign marks this as a crossing of the Continental Divide, although that is a matter of interpretation. At about is the exit for Continental Divide Road, the highest point on I-80 within the Great Divide Basin, at an elevation of . While this is no longer recognized as a crossing of the Divide, it was evidently considered to be just that during the