The Territory of Oklahoma was an organized incorporated territory of the United States that existed from May 2, 1890, until November 16, 1907, when it was joined with the Indian Territory under a new constitution and admitted to the Union as the State of Oklahoma.
The 1890 Oklahoma organic act organized the western half of Indian Territory and a strip of country known as No Man's Land into Oklahoma Territory. Reservations in the new territory were then opened to settlement in land runs later that year and in 1891 and 1893.
Seven counties were defined upon the creation of the territory. Although they were designated by number, they would eventually become Logan County, Cleveland County, Oklahoma County, Canadian County, Kingfisher County, Payne County and Beaver County. The Land Run of 1893 led to the addition of Kay County, Grant County, Woods County, Garfield County, Noble County, and Pawnee County. The territory acquired an additional county through the resolution of a boundary dispute with the U.S. state of Texas, which today is split into Greer County, Jackson County, Harmon County, and part of Beckham County.
Oklahoma Territory's history began with the Indian Intercourse Act of 1834 when the United States Congress set aside land for Native Americans. At the time, the land was unorganized territory that consisted of the federal land "west of the Mississippi and not within the states of Missouri and Louisiana, or the territory of Arkansas..." By 1856, the territory had been reduced to approximately the modern-day borders of the State of Oklahoma, except for the Oklahoma Panhandle and Old Greer County. These lands became known as Indian Territory, as they had been granted to certain Indian nations under the Indian Removal Act, in exchange for their historic territories east of the Mississippi River.
Until this point, Native Americans had exclusively used the land. In 1866, after the American Civil War, the federal government required new treaties with the tribes that had supported the Confederacy, and forced them into land and other concessions. As a result of the Reconstruction Treaties, The Five Civilized Tribes were required to emancipate their slaves and offer them full citizenship in the tribes if they wanted to stay in the Nations. This forced many of the tribes in Indian Territory into making concessions. The US officials forced the cession of some 2,000,000 acres (8,100 km2) of land in the center of the Indian Nation Territory. Elias C. Boudinot, then a railroad lobbyist, wrote an article published an article in the Chicago Times on February 17, 1879, that popularized the term Unassigned Lands to refer to this tract. Soon the popular press began referring to the people agitating for its settlement as Boomers. To prevent settlement of the land by European-Americans, President Rutherford B. Hayes, issued a proclamation forbidding unlawful entry into Indian Territory in April 1879.