There are 15 counties in Arizona. Maricopa County, with its population of 4,410,824 as of 2019, is the most populous county located within the state of Arizona. Since the time of the last U.S. census in 2010, Maricopa County, home of Phoenix, has seen an increase in the total population of the county of 15.31%. Other major counties after Maricopa County are Pima County (1,039,073) with the city of Tuscon, Pinal County (447,138), Yavapai County (231,993), Yuma County (212,128), and Mohave County (209,550). All of these counties have experienced population growth since 2010 with the greatest growth in Pinal County at 17.81%.
Greenlee County has the fewest residents in the state of Arizona with a population of 9,483. Since the 2010 United States census, Greenlee County’s population has experienced a growth rate of 13.81%. Behind Greenlee County, other counties under 50,000 residents in Arizona are La Paz County (21,098), Graham County (38,072), and Santa Cruz County (46,511). All of these counties except Santa Cruz County (-1.92%) have experienced growth, but none as high as Greenlee County.
Pinal County, with its growth rate of 17.81% since the 2010 U.S. census, is the fastest-growing county in Arizona. As of 2019, Pinal County has a population of 447,138, making it the 3rd most populous county in the state. Behind Pinal County is Maricopa County (15.31%), Greenlee County (13.81%), and Yavapai County (9.96%). The county with the lowest rate of growth, a decrease of 3.83%, is Cochise County.