Populated by Native Americans, the area that was to become the state of Oklahoma was practically unknown to Americans at the time of the Louisiana Purchase of 1803. Believing those unsettled lands to be of little value, the government set them aside as "Indian Territory" in 1830, assigning a portion to each of the Five Civilized Tribes. Between 1830-1846, 20,000 Creeks of Georgia and Alabama, 5,000 Choctaws of Mississippi and Louisiana, 4,000 Chickasaws of Mississippi, and 3,000 Seminoles of Florida were forced to move to Oklahoma. In 1838, some 16,000 Cherokees were marched west from their lands in North Carolina, Tennessee, and Georgia by troops under the command of General Winfield Scott. Many hid out in the hills and swamps of their homeland, where their descendants still remain. About one-fourth of those forced west over this "Trail of Tears" died en route of hunger, disease, cold, and exhaustion. But those who reached the Indian Territory were soon running their own affairs with skill and determination. By 1890, 67 different tribal groups resided in Oklahoma. Today Oklahoma has the largest Native American population in the United States.

As the nation moved west, settlers squatted in the Indian Territory, wanting the land for their own. On April 22, 1889, portions of the land were opened for settlement. In the next few years all unassigned Oklahoma land was opened by a series of six "runs." People who jumped the gun were called "Sooners," hence Oklahoma's nickname, the "Sooner State." Close to 17 million acres of land in the state were settled in this way; the last "lottery," a form of run, took place on August 16, 1901. Previously unsettled tracts became cities within eight hours.

Oklahoma produces many millions of barrels of oil a year and great quantities of natural gas. It is a leader in coal production and also produces gypsum limestone, tripoli, granite, and other minerals. The state's three largest industries are agriculture, tourism, and petroleum. The McClellan-Kerr Arkansas River Navigation System has given Oklahoma a direct water route to the Mississippi River and to the Gulf of Mexico. The ports of Muskogee, on the Arkansas River, and Catoosa, on the Verdigris River, connect Oklahoma to the inland waterway system and to major US markets.

Oklahoma is developing its recreational resources at a rapid rate. Every year millions of tourists and vacationers visit the growing number of lakes, built mostly for electric power, and the state park system, one of the best in the country.