Clayton is a town in Union County, New Mexico, United States. The population was 2,524 at the 2000 census. It is the county seat of Union County. Tourists heading from Texas to Colorado often pass through Clayton, which is located in the northeast corner of New Mexico. Clayton is named for a son of U.S. Senator Stephen W. Dorsey, an Arkansas Republican, originally from Ohio, who served during Reconstruction. The town was established in 1887. Trade caravans and homesteaders traveling through the Cimarron Cutoff of the Santa Fe Trail passed through Clayton. The town was a livestock shipping center for herds from the Pecos River and the Texas Panhandle.