 His original plan had been to ascend the Missouri and then the Yellowstone rivers, but information provided by these men regarding the hostility of the Blackfoot on the upper Missouri caused him to change course and cross to the Columbia by land.Hunt purchased horses from the Arikara tribe near present-day Pierre, South Dakota and began the long trek over land westward.The party passed along the borders of the Black Hills and Bighorn mountains then crossed the Wind River mountains into the valley of the Green River by way of Union Pass.