Union County is the northeastern most county in New Mexico.
The county was formed in 1894 and borders Colorado to the north, and Oklahoma and Texas to the east. Created by an act of the territorial legislation, the county was officially recognized on January 1, 1894 when the first slate of elected county officials were sworn in to office. The county is named “Union” because the citizens were united in their desire for the creation of a new county out of three existing NM counties. History has it that Thomas Edward “Black Jack” Ketchum is the only person hanged in Union County.
Clayton is the county seat and named for a son of U.S. Senator Stephen W. Dorsey of Arkansas. The population in the county is approximately 4,183 covering a total area of 3,831 square miles.