Short answers, pulled from the story.
Indian Territory was a historic sovereign territory set aside for Native American nations that existed from 1834 to 1907. The United States established general borders for this new territory through the Indian Intercourse Act of 1834. Oklahoma statehood arrived in November 1907 effectively extinguishing Indian Territory.
President Andrew Jackson formulated the policy of Indian removal with the passage of the Indian Removal Act in 1830. This policy led to events like the Trail of Tears beginning during Choctaw removals starting in 1831. The Cherokee Trail of Tears followed the ratification of the Treaty of New Echota in April 1834.
Brigadier General Stand Watie became the last Confederate general to surrender near Doaksville on the 23rd of June 1865. The Southern Treaty Commission rewrote treaties with tribes that sided with the Confederacy after the Civil War. These replacement treaties reduced the territory of the Five Civilized Tribes and provided land to resettle Plains Native Americans.
Choctaw Nation Chief Kiliahote suggested giving Indian Territory the name Oklahoma in 1866 during treaty negotiations. President Roosevelt signed the Oklahoma Enabling Act the 16th of June 1906 empowering residents to elect delegates to a state constitutional convention. Oklahoma statehood arrived in November 1907 effectively extinguishing Indian Territory.
The Cherokee Nation established its capital in Tahlequah while Chickasaw Nation chose Tishomingo later moving to Ada. Choctaw Nation built their capitol at Tuskahoma in 1884 before moving to Durant. Creek Nation set up headquarters in Okmulgee and Seminole Nation in Wewoka.