The area forming Atoka County was part of the Choctaw Nation after the tribe was forced to relocate in the early 1830s to Indian Territory from its home in the Southeastern United States. Unlike the State of Oklahoma, whose county boundaries follow the precise north–south, east–west grid established with the state's township and range system, the Choctaw Nation established its internal divisions using easily recognizable landmarks, such as mountains and rivers, as borders. The territory of present-day Atoka County fell within the Pushmataha District, one of the three administrative super-regions comprising the Choctaw Nation. Within that district, it was in parts of Atoka, Blue, and Jack's Fork counties.