While the Nuche mostly lived in the mountains and high valleys of present-day Colorado, the Cheyenne and Arapaho lived on the Great Plains and along the Front Range, occasionally venturing to the High Country. More white immigrants began crossing the plains in the 1840s and 1850s. As a result, the Cheyenne and Arapaho, as well as other Indigenous nations cut through by wagon trails, felt pressure on their resources and began attacking immigrant settlers. To reduce the risk of attack on the Overland Trail in present-day Colorado, the US government brokered the Treaty of Fort Laramie in 1851. It guaranteed Cheyenne and Arapaho sovereignty in exchange for the free passage of whites and the construction of American forts along the trail.