Maricopa County (/ˌmærᵻˈkoʊpə/ MARR-i-KOH-pə) is a coonty locatit in the sooth-central pairt o the U.S. state o Arizona. As o the 2010 census, its population wis 3,817,117, makkin it the maist populous coonty in the state, an the fowert-maist populous in the Unitit States. It is mair populous nor 23 states. The coonty seat is Phoenix, the state caipital an saxt-maist populous ceety in the kintra.