Clarendon, on U. S. Highway 287 in central Donley County, is the county seat and chief commercial and shipping center of the county. Rev. Lewis Henry Carhart, a Methodist minister, promoted the colonization of the town through a partnership with his brother-in-law, Alfred Sully, of New York. The promoters bought railroad land scrip entitling them to 343 sections of land, most of which was in Donley County. In 1878 the Clarendon Land Investment and Agency Company, an English firm, began backing Carhart. The original site of Clarendon was on a flat at the junction of Carroll Creek and the Salt Fork of the Red River. There, in the spring of 1878, Carhart and his brother-in-law, W. A. Allen, established a "Christian Colony." Although tradition maintains that Clarendon was named in honor of Carhart's wife, Clara, it has also been argued that the name was borrowed from Clarendon, England, to compliment the British backers. The townsite was platted, and construction from such available materials as rock, adobe, and pickets began immediately. A post office was opened, and stagecoach communication with Mobeetie and Tascosa established. Supplies were freighted down the cattle trails from Dodge City. Soon Carhart and his associates attracted a substantial population. The church atmosphere in Clarendon (at one time the town had seven Methodist ministers) and the absence of bars caused the rowdier Panhandle inhabitants to call it "Saint's Roost." Indeed, the first edition of Edward E. Carhart's Clarendon News (August 2, 1879) declared the town "a sobriety settlement." A public school was opened, and W. A. Allen made plans to establish a Methodist college, initially called Allenton Academy. In 1880, after L. H. Carhart left to resume his ministerial duties in East Texas, another of his brothers-in-law, attorney Benjamin Horton White, provided equally effective leadership for the colony. When Donley County was organized in 1882, Clarendon became the county seat and White was elected the first county clerk. A rock building originally used as a hotel was converted into a courthouse. White subsequently built a two-story frame hotel. Several stores, a meat market, a blacksmith shop, and a doctor's office were among the town's businesses by 1885.
In 1887, when the Fort Worth and Denver City Railway planned its line six miles south of the townsite, Clarendon's citizens voted overwhelmingly to move their homes and businesses to the tracks. Clarendon became a railroad division point and cultural center for the Panhandle, complete with an opera house. The first bank was organized in 1889, and a permanent brick-and-stone courthouse was completed in 1890. Homer Mulkey opened a photography studio in 1895. Although saloons and gambling dens flourished briefly in the Feather Hill section of town, these were shut down and cleared away in 1898 to make room for Clarendon College, which opened in the fall of that year. At about the same time, the Catholic populace built St. Mary's Academy. By then Clarendon had 200 residences, forty-six business establishments, six churches, and forty-five windmills. The town's reputation as a conservative bastion and the "Athens of the Panhandle" continued into the twentieth century.
In 1901 Clarendon was incorporated. The last legal hanging in the Panhandle occurred there on June 3, 1910. The city's independent school district purchased Clarendon College in 1927 and made it into a junior college. Since the town is located in a draw, its streets were frequently flooded until the 1930s, when the Work Projects Administration built dams and terraces to turn the water away. The building of several gins and hatcheries attested to the town's increased importance as an agribusiness center. In 1950 Clarendon had eighteen businesses, ten churches, and a population of 2,577. By then the manufacture of cotton bags and covers had been added to the local light industry. In addition, Clarendon was a manufacturing center for farm and road equipment and leather goods. The population decreased from 2,172 in 1960 to 1,974 in 1970. In 1980 Clarendon had a population of 2,220 and seventy business establishments. Clarendon Lake is located to the northeast, and a small municipal airport is located southeast of town. Clarendon was once home to the Clarendon Press, longtime publisher of western Americana. The two-story ranch home and studio of Clarendon's most famous citizen, western artist-illustrator Harold Dow Bugbee, which was built by his father in 1912, is northeast of town. Pete Borden's Boot and Saddle Shop contains an antique gun collection. The Donley County Museum features prehistoric specimens of local "Clarendonian Age" fossil beds, in addition to geological and historical artifacts. The original Saint's Roost townsite was inundated in 1968 by Greenbelt Reservoir. At that time the old cemetery was moved south on State Highway 70. In 1990 the population of Clarendon was 2,067, and in 2000 it was 1,974. In 2010 the population was 2,026 and in 2017 it was estimated at 1,878.