From: e-referencedesk- Oklahoma History Timeline

16th Century

1541 - Francisco Vásquez de Coronado first explored the region for Spain

19th Century

1803 - The US acquired most of Oklahoma in 1803 in the Louisiana Purchase from France

1819 - Adams-Onís Treaty with Spain defined Oklahoma as the southwestern boundary of the United States.

1824  - Fort Gibson was the first fort to be established in Oklahoma.

1830s - 1840s - The Cherokee, Chickasaw, Choctaw, Creek and Seminole (called the Five Civilized Tribes) are encouraged and then forced to relocate from their native lands (by the US government) into Oklahoma, known then as the Indian Territory. Thousands of native Americans lost their lives on the bloody marches to Oklahoma.

1834 - Set aside as Indian Territory

1842 - Remaining Seminole Indians (from Florida) move to Oklahoma
1845 - Western Panhandle region became US territory with the annexation of Texas
1860s - After the Civil War, because the Indians had sided with the Confederacy, they faced ruin and forfeiture of their lands
1870s - An additional 25 tribes were moved to Oklahoma to reside on federal lands
1870 - 1872 - First railroad to cross Oklahoma was built between 1870 and 1872

1889 -

• Land in Indian Territory was opened to white settlement by land runs, lotteries, and auctions. The territory was split in half, and the western half became Oklahoma Territory. 
• The first land run was held April 22nd. At exactly noon, a cannon boom signaled the start of the run which opened the Unassigned Lands for settlement.

1890 - May 2 - Region was divided into Indian Territory and Oklahoma Territory

1891 -September 21 - The Sac and Fox, Pottawatomie-Shawnee Lands, located just east of the original run site, were opened.

1892 - April 19 - The Cheyenne and Arapaho lands in western Oklahoma were opened.

1893 -September 16 - The largest and most spectacular run in northern Oklahoma, the Cherokee Strip, was held.

1895 -May 23rd - the Kickapoo Land Run was held in central Oklahoma

20th Century

1907 - November 16 - Indian Territory and Oklahoma Territory were combined to make a new state, Oklahoma. Oklahoma became the 46th state to join the Union.

1930's - Oklahoma part of the Dust Bowl

1935 - May - Rural Electrification Administration established

1937 - Route 66 which is also known as "The Mother Road," "The Main Street of America" and "The Will Rogers Highway" was paved end to end.
1990 - Oklahoma's Native American population is the largest in the nation -252,420

1959 - Alcohol prohibition is repealed in the state
1971 - Opening of the Oklahoma portion of the Arkansas River Navigation System gave the cities of Muskogee and Tulsa (at its port Catoosa) direct access to the sea.

1990 - Oklahoma becomes the first state to limit the terms of legislators 
1995 - Terrorist bomb blows up the Murrah Federal Building in downtown Oklahoma City, killing 168 people, and injuring hundreds more.