As of the 2020 census, the city population was 12,965, an increase of 13.3% from 11,442 in 2010, and represents more than half of the population of the county, along with being the largest city in the Oklahoma Panhandle. Guymon ( / ˈ ɡ aɪ m ə n/ GHY-mən) is a city and county seat of Texas County, in the panhandle of Oklahoma, United States.