the 1851 treaty of fort laramie between the united states and various tribes including the cheyenne and arapaho says that the cheyenne and arapaho were supposed to have a very big amount of territory in the area between the north platte river and arkansas river and eastward from the rocky mountains to western kansas. this area included present-day southeastern wyoming, southwestern nebraska, most of eastern colorado, and the westernmost parts of kansas. however, in november 1858, people found gold in the rocky mountains in colorado (then part of the western kansas territory). this created a gold rush. a lot of white people went across cheyenne and arapaho lands. colorado territory officials asked federal authorities to change the size of indians lands in the treaty. in fall 1860, a.b. greenwood, commissioner of indian affairs, came to bent's new fort along the arkansas river to make a new treaty.