Marshall county was once part of the Chickasaw Nation and at one time part of the area known as Pickens County, Indian Territory. It is located in southern Oklahoma with Madill serving as the county seat.

The county is bounded on the east by Lake Texoma and on the south by the Red River. Recreational facilities can be found at Lake Texoma Resort Park in the southeast part of the county.

History buffs will want to take in visits to the Worth Hotel and the Marshall County Courthouse in Madill and Haley's Point Site in Lebanon.

The county population on July 1, 1999, was 12,377, an increase of 1,548 over the 1990 census.