The county is in the Coastal Plains physiographic region, and is drained mostly by the Blue River. The Washita River originally drained much of the western part of the county, but now empties into Lake Texoma, which forms much of the southern boundary of the county. The county is a major part of the Texoma region.
The county is in the Coastal Plains physiographic region, and is drained mostly by the Blue River. The Washita River originally drained much of the western part of the county, but now empties into Lake Texoma, which forms much of the southern boundary of the count.y. The county is a major part of the Texoma region