Flagstaff is a city in northern Arizona, in the southwestern United States. In 2015, the city's estimated population was 70,320. Flagstaff's combined metropolitan area has an estimated population of 139,097. It is the county seat of Coconino County. The city is named after a ponderosa pine flagpole made by a scouting party from Boston (known as the "Second Boston Party") to celebrate the United States Centennial on July 4, 1876.