In the early part of the 19th century, Oklahoma was lightly populated. The federal government wanted to move Indians who occupied valuable land in the southeast onto land that was less in demand. They eventually pressured the Five Civilized Tribes — the Choctaw, Cherokee, Chickasaw, Creek, and Seminole — into giving up their homelands in exchange for land in Oklahoma. Each of the five nations migrated to the new lands, which were called Indian Territory. Although the land was supposed to be theirs in perpetuity, the Indians gradually lost it. During the Civil War, the Civilized Tribes had supported the Confederacy. Following the war, Congress punished the tribes by forcing them to give up the western section of their territory. Pressure from white settlers persuaded the federal government to negotiate a series of treaties, under which the Indians relinquished their land. Several great land rushes, in which would-be settlers stormed into newly opened lands, took place. The largest was on September 16, 1893, when more than 50,000 people claimed land on the first day. Not everyone was content to wait for the starter's pistol and made their way into the territory in advance to stake out their claims. Those people went "sooner" rather than later, giving them the nickname "Sooners." Oklahoma became the 47th state in 1907 and became known as the Sooner State. Although the first settlers were looking for prime agricultural land, much of Oklahoma's prosperity has depended on what was deep beneath it. The first small oil well was drilled in 1889, and a significant discovery was made at Bartlesville in 1897. Tulsa became the center of Oklahoma's petroleum industry.