Captain Wyeth started on west on August 6, 1834. At Fort Hall he left Robert Evans in charge, with the following men to assist him in organizing the business and encouraging trapping and trading in the vicinity: Robert Cairnes, Thomas Callahan, John Hynds, John Maxwell, Samuel Nott, William Richmond, Peter Rost, Osborne Russell, Charles Schriver, John Timmer, and John Ward. The presence of several hundred Bannock and Shoshone Indians camped with their families in the general vicinity of the fort seemed a good omen for the future of the post.
But the Hudson's Bay Company had other plans. Thomas McKay, a tried and true HBC man, had traveled for a time with Wyeth and was probably fully aware of Wyeth's plans. Soon a Hudson's Bay party was building a trading post of their own near the junction of Boise River with the Snake. They named the post Fort Boise, its purpose was simply to drive Fort Hall out of business. This they proposed to do using the almost limitless resources of the great English company to overbid Wyeth in the payment for furs and underbid him in the sale of goods to the Indians. This policy worked and Wyeth was never able to make a decent profit from the Fort Hall business.
In 1837 Wyeth sold out to the Hudson's Bay Company at a loss of about $30,000. The English company's banner replaced the Stars and Stripes at Fort Hall and remained there until the US gained possession by treaty with England giving us all the Oregon Country south of the forty-ninth parallel in exchange for part of the Pacific Northwest beyond the 49th parallel all the way north to the southern boundary of territory claimed by Russia.
In 1843, the "Great Migration" to the Willamette Valley of Oregon began. Dr. Marcus Whitman, who had established a mission near Walla Walla, Washington, made a trip to the East and led a train of about 200 wagons, about 875 emigrants, with hundreds of head of livestock, back to Fort Hall. There Captain Grant, the HBC trader in charge, tried in vain to persuade the emigrants to leave their wagons, as had been the usual procedure. Still using their wagons, the emigrants finally reached the Dalles on the Columbia River, and this accomplishment, more than any other single factor, clinched for the United States ownership of the Oregon Country now included in Idaho, Oregon, Washington, Montana and Wyoming west of the Continental Divide.