Oklahoma's four main mountain ranges include the Ouachitas, Arbuckles, Wichitas, and the Kiamichis. In addition to several smaller ranges, Oklahoma also notably encompasses a portion of the Ozarks.

The state's highest peak, 4,973 feet (1,515 m) Black Mesa, resides in the far northwestern corner of the panhandle near the town of Kenton. The lowest elevation in the state is in the far southeastern corner, near Idabel, at 324 feet (99 m). Oklahoma also has what is officially considered the highest hill in the world, Cavanal Hill, at 1,999 feet (609 m); this is considering the fact that a "mountain" is anything 2,000 feet or higher. It is located in Poteau, Oklahoma.[5]

With 200 man-made lakes, Oklahoma has more man-made lakes than any other state and boasts over one million surface-acres of water and 2,000 more miles (3,200 km) of shoreline than the Atlantic and Gulf coasts combined. Lake Eufaula is the largest lake in the state, covering 102,000 surface acres (413 km²) of water.

Prior to becoming a state in 1907, Oklahoma was designated the Indian Territory by the U.S. government. This was done in order to provide a place for the Native Americans to relocate to as the United States expanded westward towards the Mississipi River in the 1800's. The Indian Removal Act of 1830 was signed by President Andrew Jackson within a year of taking office. This act gave the President the power to negotiate treaties for removal with Indian tribes living east of the Mississippi River. The treaty called for the Indians to give up their eastern land for land in the west. Those who wished to stay behind were allowed to stay and become citizens in their state. For the tribes that agreed to Jackson's terms, the removal was peaceful; however, those who resisted were eventually forced to leave. The northern Indian tribes included the Shawnee, Ottawa, Potawatomi, Sauk, and Foxes. Because of their size and fragmentation, relocation was easier than that of the southern tribes, which were much larger and more civilized. The Choctaw, Creek, Chickasaw, Seminole, and Cherokee tribes (the Five Civilized Tribes) living in the Southern United States were considered civilized because of their adoption of Western customs and in the case of the Cherokee, the development of a written language, as well as having good relationships with their neighbors. The Choctaw signed relocation treaties in September 1830, notably the Treaty of Dancing Rabbit Creek. Those Choctaws that decided to stay in Mississippi were soon forced off of their ancestral lands and moved west. The Creek also refused to relocate and signed a treaty in March 1832 to open up a large portion of their land in exchange for protection of ownership of their remaining lands. The United States failed to protect the Creeks, and in 1837, they were militarily removed without ever signing a treaty.

After the American Civil War, in 1866, the federal government forced the tribes into new treaties. Most of the land in central and western Indian Territory was ceded to the government. Some of the land was given to other tribes, but the central part, the so-called Unassigned Lands, remained with the government. Another concession allowed railroads to cross Indian lands. Furthermore the practice of slavery was outlawed. Some nations were integrated racially and otherwise with their slaves, but other nations were extremely hostile to the former slaves and wanted them exiled from their territory. In the 1870s, a movement began by people wanting to settle the government lands in the Indian Territory under the Homestead Act of 1862. They referred to the Unassigned Lands as Oklahoma and to themselves as Boomers.

In the 1880s, early settlers of the state's very sparsely populated Panhandle region tried to form the Cimarron Territory but lost a lawsuit against the federal government. This prompted a judge in Paris, Texas, to unintentionally create a moniker for the area. "That is land that can be owned by no man," the judge said, and after that the panhandle was referred to as No Man's Land until statehood arrived decades later. In 1884, in United States v. Payne, the United States District Court in Topeka, Kansas, ruled that settling on the lands ceded to the government by the Indians under the 1866 treaties was not a crime. The government at first resisted, but Congress soon enacted laws authorizing settlement.

During the height of the Great Depression, drought and poor agricultural practices led to the Dust Bowl, when massive dust storms blew away the soil from large tracts of arable land and deposited it on nearby farms and ranches, distant states, the Atlantic Ocean, and even occasionally Great Britain. The resulting crop failures forced many small farmers to flee the state altogether. Although the most persistent dust storms primarily affected the Panhandle, much of the state experienced occasional dusters, intermittent severe drought, and occasional searing heat. Towns such as Alva, Altus, and Poteau each recorded temperatures of 120°F (49°C) during the epic summer of 1936. Advances in agro-mechanical technology simultaneously enabled less labor-intensive crop production. Many large landowners and planters had more labor than they needed with the new technology, and the federal Agricultural Adjustment Act paid them to reduce production. Plantation owners throughout the American South and much of eastern and southern Oklahoma released their sharecroppers of their debts and evicted them. With few or no local opportunities available for them, many emancipated, but destitute blacks and whites fled to the relative prosperity of California to work as migrant farm workers and, after the onset of World War II, in factories.

Major trends in Oklahoma history after the Depression era included the rise again of tribal sovereignty (including the issuance of tribal automobile license plates, and the opening of tribal smoke shops, casinos, grocery stores, and other commercial enterprises), the building of Tinker Air Force Base, the rapid growth of suburban Oklahoma City and Tulsa, the drop in population in Western Oklahoma, the oil boom of the 1980s and the oil bust of the 1990s.

The state's judicial branch consists of the Oklahoma Supreme Court, the Court of Criminal Appeals, and 77 District Courts which serve one county apiece. The Oklahoma judiciary also contains two independent courts: a Court of Impeachment (which is the Senate sitting) and the Oklahoma Court on the Judiciary. Oklahoma is unusual in that it has two courts of last resort, the state Supreme Court hears civil cases, and the state Court of Criminal Appeals hears criminal cases (the state of Texas uses a similar system). Judges of those two courts, as well as the Court of Civil Appeals are appointed by the Governor upon the recommendation of the state Judicial Nominating Commission, and are subject to a non-partisan retention vote on a six-year rotating schedule.

The state is divided into 77 counties which deliver local government. Each is governed by a three member commission. Other county elected officials are the tax assessor, clerk, court clerk, treasurer, and sheriff. Cities and towns are established under the rights granted in the Oklahoma statutes (in comparison, Oklahoma gives municipal governments a great deal of latitude in chartering new governments). Towns are municipalities of under 1000 residents, while cities have more than 1000 residents. Major cities are also allowed to form "charter governments," in which the voters choose the form of government they want to use in place of the statutory forms. Other local government units in Oklahoma include independent and dependent school districts, Technology Center Districts (once known as VOTECH), community college districts, rural fire departments, rural water districts, and other special use districts.

Oklahoma City is a primary economic engine of the state, centered on the finance, retail, governance, entertainment, and tourism sectors. The city has numerous manufacturing and processing plants as well as a growing biotech research and health center. Oklahoma City has a large aviation market and its location at the intersection of I-35, I-40, and I-44 makes Oklahoma City an important distribution point. Oklahoma City is home to many corporate and regional headquarters including Devon Energy, Chesapeake Energy, Sonic Drive-In, AT&T, The Hertz Corporation, BancFirst, OGE Energy, Midfirst Bank, Hobby Lobby, Dobson Communications, Express Personnel Services, Oklahoma Publishing Company, Globe Life and Accident Insurance, AOL, Pre-Paid Legal Services, Inc., and Big Daddy's BBQ Sauce.

Tulsa is another primary economic engine of the state, centered on energy, aerospace, telecommunications, and transportation. The city has the nation's most inland sea port and Oklahoma's only connection to the ocean, the Tulsa Port of Catoosa [2], which connects the state with international ocean trade routes through the Arkansas River and Mississippi River. Despite an oil bust that plagued the entire state in the 1980's, Tulsa is still among the top cities in the nation for the number of oil and energy related company headquarters. Tulsa is also home to an extensive aviation market, exemplified by its American Airlines maintenance center, the largest airline maintenance base in the world. Recently, Forbes magazine rated Tulsa as second in the nation in job income growth, and one of the best 50 cities to do business in the country.