Following the return of the Corps of Discovery in 1806, reports of abundant beaver near the confluence of the Gallatin, Jefferson, and Missouri rivers drew fur traders including Manuel Lisa, Andrew Henry, and Pierre Menard to the headwaters, and in 1809 they formed the Missouri Fur Company to establish a fort there. In March 1810, thirty-five fur trappers guided by Lewis and Clark Expedition veterans John Colter and George Drouillard reached the headwaters in April 1810 and built Three Forks Post, possibly between the Madison and Jefferson about two miles above the rivers' confluence. Although intended to protect trappers from local tribes, especially the Blackfeet, the post offered little safety in territory where the Blackfeet opposed American trapping. The first attack came eight days after the post was built, killing two trappers while three other men disappeared, and in early May the Blackfeet killed and mutilated George Drouillard. Despite the area's plentiful resources, the danger proved too great, and after three months the Missouri Fur Company abandoned the post, which the Blackfeet then burned. John Colter, a veteran of the Lewis and Clark Expedition who left the Corps' service in August 1806 to explore and trap for the Missouri Fur Company, became one of the headwaters area's best-known mountain men. While trapping along the Jefferson River in 1809, Colter and John Potts were surrounded by Blackfeet; Potts was killed after he shot a member of the tribe, and Colter, stripped naked and given a short head start, ran for his life for about five to six miles before turning on his nearest pursuer, taking his spear, killing him, and hiding in the Madison River beneath a driftwood dam or beaver lodge until nightfall. More than a week later, sunburned, hungry, and swollen, he reached Fort Manuel Lisa at the confluence of the Yellowstone and Big Horn rivers more than 200 miles east. After returning to the area with the Missouri Fur Company in 1810, Colter departed after just eleven days, saying that after his close call with the Blackfeet the year before he had promised never to return; he left the headwaters for good and died of jaundice in St. Louis three years later.