There is evidence—chiefly from the Spiro Mound in eastern Oklahoma, excavated in 1930—that an advanced Indian civilization inhabited the region around AD 900–1100. By the time the Spanish conquistadores, led by Hernando de Soto and Francisco Vasquez de Coronado, arrived there in the 16th century, however, only a few scattered tribes remained. Two centuries later, French trappers moved up the rivers of Oklahoma.
Except for the panhandle, which remained a no-man's-land until 1890, all of present-day Oklahoma became part of US territory with the Louisiana Purchase in 1803. Under the Indian Removal Act of 1830, Indian tribes from the southeastern US were resettled in what was then known as Indian Country. Although 4,000 Indians died along the "Trail of Tears" (from Georgia to Oklahoma) between the time of removal and the Civil War, the Five Civilized Tribes—Cherokees, Chickasaw, Choctaw, Creek, and Seminole—prospered in the new land. The eastern region that they settled, comprising not quite half of modern Oklahoma and known as Indian Territory since the early 19th century (although not formally organized under that name until 1890), offered rich soil and luxurious vegetation. White settlers also came to farm the land, but their methods depleted the soil, preparing the way for the dust bowl of the 1930s. Meanwhile, the increasing movement of people and goods between Santa Fe and New Orleans spurred further growth in the region. Military posts such as Ft. Gibson, Ft. Supply, and Ft. Towson were established between 1824 and the 1880s, with settlements growing up around them.
During the early Civil War period, the Five Civilized Tribes—some of whose members were slaveholders—allied with the Confederacy. After Union troops captured Ft. Gibson in 1863, the Union Army controlled one-half of Indian Territory. From the end of the Civil War to the 1880s, the federal government removed the eastern tribes from certain lands that were especially attractive to the railroads and to interested white settlers. Skirmishes between the Indians and the federal troops occurred, culminating in a massacre of Cheyenne Indians on 27 November 1868 by Colonel George Custer and his 7th Cavalry at the Battle of the Washita.
Amid a clamor for Indian lands, Congress opened western Oklahoma—formerly reserved for the Cherokee, Cheyenne, Fox, and other tribes—to homesteaders in 1889. Present-day Oklahoma City, Norman, Guthrie, Edmond, and Stillwater represent the eastern boundary for the 1889 "run" on Oklahoma lands; eight more runs were to follow. The greatest was in 1893, when about 100,000 people stormed onto the newly opened Cherokee outlet. The drive to get a land claim was fierce, and thousands of "Sooners" staked their claims before the land was officially opened. The western region became Oklahoma Territory, governed by a territorial legislature and a federally appointed governor in 1890; Guthrie was named the capital. Most of eastern Oklahoma continued to be governed by the Five Civilized Tribes.
Although an Oklahoma statehood bill was introduced in Congress as early as 1892, the Five Civilized Tribes resisted all efforts to unite Indian Territory until their attempt to form their own state was defeated in 1905. Congress passed an enabling act in June 1906, and Oklahoma became the 46th state on 16 November 1907 after a vote of the residents of both territories. Oklahoma City was named the state capital in 1910.
When President Theodore Roosevelt signed the statehood proclamation, Oklahoma's population was about 1,500,000—75% rural, 25% urban—most of them drawn by the state's agricultural and mineral resources. The McAlester coal mines had opened in 1871, and lead and zinc were being mined in Ottawa County. But it was oil that made the state prosperous. Prospecting began in 1882, and the first commercial well was drilled at Bartlesville in 1897. The famous Glenn Pool gusher, near Tulsa, was struck in 1905. Oil wells were producing more than 40 million barrels annually when Oklahoma entered the Union, and the state led all others in oil production until 1928.
Generally, the decade of the 1920s was a tumultuous period for Oklahoma. A race riot in Tulsa in 1921 was put down by the National Guard. (In February 2000, a state commission recommended that the surviving victims be compensated for what has been called the nation's most violent instance of racial oppression. The recommendation launched an intense debate over whether today's taxpayers should have to pay restitution for yesterday's crimes.) Also in 1921, the Ku Klux Klan claimed close to 100,000 Oklahomans. The Klan was outlawed when Governor John C. Walton declared martial law in 1923, during a period of turmoil and violence that culminated in Walton's impeachment and conviction on charges of incompetence, corruption, and abuse of power. The 1930s brought a destructive drought, dust storms, and an exodus of "Okies," many of them to California. Colorful Governor William "Alfalfa Bill" Murray led the call for federal relief for the distressed dust bowl region—though he insisted on his right to administer the funds. When Oklahoma oil fields were glutting the market at 15 cents a barrel, Murray placed 3,106 producing wells under martial law from August 1931 to April 1933. Kansas, New Mexico, and Texas also agreed to control their oil production and under the leadership of Governor E. W. Marland, the Interstate Oil Compact was created in 1936 to conserve petroleum and stabilize prices.
Oklahoma's first native-born governor, Robert Kerr (later a senator for 14 years) held the statehouse during World War II and brought the state national recognition by promoting Oklahoma as a site for military, industrial, and conservation projects. Under early postwar governors Roy Turner, Johnston Murray, and Raymond Gary, tax reductions attracted industry, major highways were built, a loyalty oath for state employees was declared unconstitutional, and Oklahoma's higher educational facilities were integrated. The term of Governor Howard Edmondson saw the repeal of prohibition in 1959, the establishment of merit and central purchasing systems, and the introduction of a state income tax withholding plan.
Oil and gas again brought increased wealth to the state in the 1960s, 1970s, and early 1980s, as state revenues from oil and gas increased from $72 million in 1972 to $745 million in 1982. Nearly $1 billion was spent for new highways, schools, and state offices; new police were hired; and teacher salaries were raised to nationally competitive levels. Unemployment fell to 3.6% in 1981 while an influx of job seekers from other states made Oklahoma one of the fastest-growing states in the nation in the early 1980s.
In 1983, as oil prices fell in the face of a growing worldwide oil glut, the oil boom suddenly ended. Between 1982 and 1986, jobs in the extraction of oil and gas dropped by 50%. The failure of 24 banks, home mortgage foreclosures, and mounting distress among the state's farmers added to Oklahoma's financial woes. Falling state revenues and a balanced budget requirement in the state constitution compelled Governor George Nigh in 1983 to cut appropriations and to preside over a series of tax increases that lost for Oklahoma its claim to one of the lowest tax burdens in the nation.
The oil bust did not entirely devastate the Oklahoma economy. Those industries with a national rather than a regional base, such as distribution, transportation, food processing, and light manufacturing, continued to prosper, and the state's leaders made a concerted effort to diversify Oklahoma's industries even further by attracting both private enterprise and defense contracts. By the end of the decade, the economy had begun to recover, and recovery continued into the 1990s. By 1999 the unemployment rate had dropped to 3.4%, below the national average. Poverty was on the decline in the state: 15.6% of Oklahomans lived below the federal poverty level in 1990; in 1998 the rate dipped to 14.1%. But with the 10th-lowest median income in the nation, the state's income levels lagged behind, causing some analysts to predict that Oklahoma might have problems competing in a strong economy.
On 19 April 1995, the Alfred P. Murrah Federal Building in Oklahoma City was destroyed in a bomb blast that claimed 168 lives and constituted the most serious act of terrorism in the history of the United States. Governor Frank Keating was commended for his strong leadership during the crisis. A memorial to the victims was unveiled in April 2000, the five-year anniversary of the tragedy.
In 2003 Oklahoma faced its largest budget deficit in state history ($600 million). Democratic Governor Brad Henry pledged to eliminate taxes on retirement income for senior citizens, provide access to affordable prescription drugs, retain jobs in the state, improve Oklahoma schools, and increase teachers' salaries. Henry proposed a state lottery to fund education.