Can you explain a little bit about the colonization of the west?

The Transcontinental Railroad to the West was completed in the United States after the Civil War in 1869. This opened up huge areas for settlement and economic development. White settlers from the East rushed across the Mississippi River, eager for a chance at a fresh start, and the opportunity to mine, farm, and ranch. African-American settlers also rushed at the chance of moving West, in the hopes of starting all-black towns and counties. Settlers greatly changed the landscape and ecology of the region. The herds of buffalo that once grazed were wiped out as farmers plowed the natural grasses and introduced herds of cows to the area. The loss of the buffalo and the large influx of white settlers greatly affected the lives of Native Americans. By the 1880s, most Native Americans were living on reservations. The reservations were typically in areas that were seen as less desirable by the white settlers.