The Wagons That Weren't Supposed to Make It: Bonneville's 1832 Crossing of South Pass
In the summer of 1832, a U.S. Army captain with almost no experience in the fur trade did something that seasoned mountain men had assumed was impossible. He took twenty wagons over the Rocky Mountains.
His name was Benjamin Louis Eulalie de Bonneville, and the route he pioneered through Wyoming's South Pass would become the backbone of the Oregon Trail, carrying hundreds of thousands of settlers west over the following decades.
Who Was Benjamin Bonneville?
Bonneville was born in France in 1796 and immigrated to the United States as a young child. He graduated from West Point in 1815 and spent years posted at frontier forts in Arkansas, Texas, and Indian Territory, where he watched the fur trade boom around him.
In 1832, Bonneville requested a year of leave from the Army to lead a privately funded expedition into the Rocky Mountains. On paper, it was a fur trading venture backed by financiers John Jacob Astor and Alfred Seton. In practice, historians have long debated whether Bonneville's real assignment was to gather intelligence on British activity in the far Northwest for the Army, since his leave papers spelled out exactly what kind of information he was expected to bring back.
A Novice Takes On the Mountains
Four years earlier, in 1828, fur trader William Sublette had proven that wagons could reach South Pass, but he stopped short of taking them across and went back to pack animals afterward. It took an outsider to finish the job.
Bonneville set out in the spring of 1832 with roughly 110 men and 20 wagons loaded with supplies for trappers in the Rockies. He believed wagons were more efficient than pack trains since they would save the daily labor of loading and unloading horses, and they reduced the risk of animals wandering off or spooking in the night. It was a logical argument from a man who knew far more about army logistics than beaver pelts.
Crossing South Pass
The party pushed west across present day Wyoming and reached South Pass, the broad, gently sloping gap in the Rockies that Native peoples had used for generations and that fur trappers had only recently begun to notice. Unlike the jagged peaks travelers might expect, South Pass is wide and gradual, which is exactly why it worked for wagons.
Bonneville and his party crossed the Continental Divide there in 1832, becoming the first group to take wagons over the pass. Bonneville later recalled realizing they had crossed onto the western side of the divide when his men caught trout in a mountain stream, since trout could only be found in the rivers flowing toward the Pacific.
After crossing, Bonneville pushed on to the Green River, where he built a stockaded winter camp. Heavy snow arrived earlier than expected, and the site was abandoned before winter set in, earning it the nickname Fort Nonsense. Bonneville moved his operation to the Salmon River in Idaho for the season, though the Green River site continued to serve as a rendezvous point until his party returned east in 1835.
Why It Mattered
Bonneville's wagons never should have made it, at least according to the conventional wisdom of the mountain men who came before him. But they did, and the proof mattered more than the fur trading results ever could.
Word of the crossing spread. Washington Irving, the author of Rip Van Winkle and The Legend of Sleepy Hollow, later wrote The Adventures of Captain Bonneville based on the expedition's journals, introducing the route to a much wider audience. A decade later, Lieutenant John C. Fremont's expeditions would popularize South Pass further, and by the 1840s it had become the essential gateway for Oregon Trail emigrants heading toward the Pacific Northwest.
South Pass itself still stands as one of the most significant landmarks along the emigrant trails: eighteen miles wide, gently graded, and the reason wagon travel across the continent was ever possible at all.
Keep Exploring This Story
Bonneville's improbable crossing is just one chapter in the larger story of how the American West was opened to settlement. If you want the full picture of the men, the maps, and the decisions that turned an unlikely wagon train into a national trail, our book on Bonneville's expedition digs into the details you won't find anywhere else. Pick up a copy today and follow the wagons all the way to South Pass and beyond.
