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.