Several treaties were signed early in this period to permit White Americans to send immigrants, to construct roads and to station troops along trails from the Great Plains, through the Rocky Mountains and down to the Pacific Ocean. One such agreement was the 1851 Treaty of Fort Laramie. To which established trail did it refer?

White Americans had settled both the Atlantic and the Pacific coasts, but the Great Plains in between had been hardly incorporated into the USA. Native Americans (Red Indians) occupied them, and the potential for conflict loomed seriously, as White Americans were more and more tempted to encroach on Indian lands.