Gallup is a city in McKinley County, New Mexico, United States, with a population of 21,678 as of the 2010 census. A substantial percentage of its population is Native American, with residents from the Navajo, Hopi, and Zuni tribes. Gallup is the county seat of McKinley County and the most populous city between Flagstaff and Albuquerque, along the historic U.S. Route 66.The city was founded in 1881 as a railhead for the Atlantic and Pacific Railroad, and named after David Gallup, a paymaster for the railroad. It is on the Trails of the Ancients Byway, one of the designated New Mexico Scenic Byways. Because of the nearby rugged terrain, it was a popular location in the 1940s and 1950s for Hollywood Westerns.