Pecos is the largest city in and the county seat of Reeves County, Texas, United States. It is in the valley on the west bank of the Pecos River at the eastern edge of the Chihuahuan Desert, in the Trans-Pecos region of West Texas and just south of New Mexico's border. Its population was 12,916 at the 2020 census. On January 24, 2012, Pecos City appeared on the Forbes 400 as the second-fastest growing small town in the United States.