Short answers, pulled from the story.
Indian Territory was land set aside by the United States government for the forced resettlement of Native American nations displaced from their ancestral homelands. Its initial borders were fixed by the Indian Intercourse Act of 1834, and it was located in the central United States. By 1890, successive acts of Congress had reduced it to the approximate boundaries of present-day Oklahoma.
Indian Territory was formally extinguished as a legal entity with Oklahoma statehood in November 1907. The Oklahoma Enabling Act, signed by President Theodore Roosevelt on the 16th of June, 1906, merged Indian Territory with Oklahoma Territory to form the single state of Oklahoma.
The Five Civilized Tribes were the Cherokee, Chickasaw, Choctaw, Muscogee Creek, and Seminole nations, forcibly relocated from the southeastern United States between 1814 and 1840. Each nation established a tribal capital in Indian Territory: the Cherokee at Tahlequah, the Chickasaw at Tishomingo, the Choctaw at Tuskahoma, the Creek at Okmulgee, and the Seminole at Wewoka.
The Trail of Tears refers to the forced removal of Native American nations from their homelands in the southeastern United States to Indian Territory. The Choctaw removal began in 1831 under the Treaty of Dancing Rabbit Creek, establishing the route that gave the Trail of Tears its name. The Cherokee removal followed the controversial Treaty of New Echota, signed in 1835, which the Cherokee National Council never approved.
Stand Watie was a Brigadier General in the Confederate Army and the commander of Cherokee forces in Indian Territory during the American Civil War. He became the last Confederate general to surrender in the entire war, laying down his arms on the 23rd of June, 1865, near the community of Doaksville in Indian Territory.
The Supreme Court's 2020 decision in McGirt v. Oklahoma prompted a review of tribal land status within Oklahoma and found that almost the entire eastern half of the state had remained Indian country under federal law. The ruling confirmed that the boundaries established for Indian Territory in the 19th century retained legal force even after Oklahoma statehood in 1907.