General History of the Western Indian Tribes 1851-1870 – Indian Wars
Up to 1851, the immense uninhabited plains east of the Rocky Mountains were admitted to be Indian Territory, and numerous tribes roamed from Texas and Mexico to the Northern boundary of the United States. Then came the discovery of gold in California, drawing a tide of emigration across this wide reservation, and it became necessary, by treaty with the Indians, to secure a broad highway to the Pacific shore. By these treaties the Indians were restricted to certain limits, but with the privilege of ranging, for hunting purposes, over the belt thus re-reserved as a route of travel.