Canadian County, Oklahoma in the context of El Reno, Oklahoma

Oklahoma City (/ˌoʊkləˈhoʊmə -/ OH-klə-HOH-mə -⁠), often shortened to OKC, is the capital and most populous city of the U.S. state of Oklahoma. It is the 20th-most populous U.S. city and 8th largest in the Southern United States, with a population of 681,054 at the 2020 census. The Oklahoma City metropolitan area, with an estimated 1.49 million residents, is the largest metropolitan area in the state and 42nd-most populous in the country. It is the county seat of Oklahoma County, with the city limits extending into Canadian, Cleveland, and Pottawatomie counties; however, areas beyond Oklahoma County primarily consist of suburban developments or areas designated rural and watershed zones. Oklahoma City ranks as the tenth-largest city by area in the United States when including consolidated city-counties, and second-largest when such consolidations are excluded. It is also the second-largest state capital by area, after Juneau, Alaska.

Oklahoma City has one of the world's largest livestock markets. Oil, natural gas, petroleum products, and related industries are its economy's largest sector. The city is in the middle of an active oil field, and oil derricks dot the capitol grounds. The federal government employs a large number of workers at Tinker Air Force Base and the United States Department of Transportation's Mike Monroney Aeronautical Center (which house offices of the Federal Aviation Administration and the Transportation Department's Enterprise Service Center, respectively).

The Oklahoma City metropolitan area is an urban region in Central Oklahoma. It is the largest metropolitan area in the state of Oklahoma and contains the state capital and principal city, Oklahoma City. It is often known as the Oklahoma City Metro (sometimes shortened to simply "the Metro"), or Greater Oklahoma City in addition to the nicknames Oklahoma City itself is known for, such as OKC or "the 405".

Counties in the Oklahoma City metropolitan area include Canadian, Cleveland, Grady, Lincoln, Logan, McClain, and Oklahoma. According to the 2020 U.S. census, the metropolitan region had a population of 1,425,695, up from 1,083,346 at the 2000 census.

The Land Rush of 1889 was the first land run into the Unassigned Lands of the former western portion of the federal Indian Territory, which had decades earlier since the 1830s been assigned to the Creek and Seminole native peoples. The area that was opened to settlement included all or part of the Canadian, Cleveland, Kingfisher, Logan, Oklahoma, and Payne counties of the present-day U.S. state of Oklahoma. The land run started at high noon (12:00 pm) on April 22, 1889. An estimated 50,000 people were lined up at the start, seeking to gain a piece of the available two million acres (8,100 km).

The Unassigned Lands were considered some of the best unoccupied public land in the United States. The Indian Appropriations Act of 1889 was passed and signed into law with an amendment by congressman William McKendree Springer authorized 23rd President Benjamin Harrison, to open the two million acres (8,100 km) of the western portion of the remaining Indian Territory (established in 1834 with a much greater allotment set aside for the southeastern native tribes of extensive lands of the previous Louisiana Purchase of 1803, west of the Mississippi River), during the administration of 7th President Andrew Jackson (1767-1845, served 1829-1837).

On a simple east/west basis, Western Oklahoma is popularly considered that part of the state west of I-35. I-35 creates a north/south line through the approximate center of the main body of the state (i.e., without regard for the Oklahoma Panhandle), passing through Oklahoma City, the state capital.

However, other definitions are possible. For tourism purposes, the Oklahoma Tourism and Recreation Department breaks the state into six regions. The 14 counties of Southwest Oklahoma, called Great Plains Country, do all fit west of I-35, including the easternmost counties in the grouping, Stephens and Jefferson. But, while most of the 16 counties of Northwest Oklahoma, called Red Carpet Country, are also west of I-35, the two easternmost in that grouping, Kay and Noble, each have some land area east of I-35. Then, the department includes 12 counties in Central Oklahoma, called Frontier Country, around Oklahoma City. Portions of that grouping, like Canadian County, are entirely west of I-35. And, the department has established a South Central grouping of 7 counties, called Chickasaw Country, some of which, like Carter County, have more land west of I-35 than east.