Flagstaff, AZ has a population of 69,270 and is the 528th largest city in the United States. The population density is 1,050 per sq mi which is 1726% higher than the Arizona average and 1059% higher than the national average. The median age in Flagstaff is 25 which is approximately 32% lower than the Arizona average of 37. In Flagstaff, 35% of the population over 15 years of age are married, 82% speak English and 10% speak Spanish. 46% of Flagstaff residents were born in Arizona, 47% were born out of state, 1% were born outside of the United States and 7% were foreign born.