Roger Mills county, originally part of the Cheyenne-Arapaho reservation, is located in western Oklahoma on the Texas border with Cheyenne serving as the county seat. It is named in honor of Roger Mills, a popular and distinguished Texas congressman.
The county is home to the historically significant Washita Battle Site as well as the Black Kettle National Grassland and the Black Kettle Museum. Other interesting sites within the county include the Goodwin-Baker Archeological Site near Berlin and the Dorroh-Trent House in Hammon.
Major waterways in the county include the Canadian River, which forms the northern line with Ellis County and the Washita River which flows through the Grassland on its way east to Foss Lake in Custer County.
The county population on July 1, 1999, was 3,593, a decrease of 554 over the 1990 census.