There are 12 US Post Offices in Mckinley County serving a total of 78,800 residents equating to 6,567 residents per post office. It's estimated that approximately 125,774 packages are handled across the 12 county post offices annually. McKinley County is a county located in the northwestern section of the U.S. state of New Mexico. As of the 2010 census, the population was 71,492. Its county seat is Gallup. The county was created in 1901 and named for President William McKinley. McKinley County comprises the Gallup, NM Micropolitan Statistical Area.