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.

In 1872, the Missouri-Kansas-Texas Railway (nicknamed the Christopher Casey) built a track through the county.

[3] The economy of Atoka County has been largely built on coal mining, limestone quarrying, forestry, and agriculture.

A major employer is the Oklahoma State Penitentiary Farm (renamed the Mack H. Alford Correctional Center), a medium-security prison that opened in 1933.

The Ouachita Mountains are in the eastern part of the county, while the Sandstone Hills and Coastal Plains physiographic regions provide a more level terrain suitable for agriculture in the north and western part of the county.

[3] About 12 miles WSW of the town of Atoka is Boggy Depot State Park, the historic site of a once large community on the Butterfield Overland Mail stagecoach route.

The Katian Age of the Ordovician Period of geological time is named for Katy Lake, which is two miles north east of Atoka.

[19] The following sites in Atoka County are listed on the National Register of Historic Places: