<page_title> List of the most populous counties in the United States </page_title> <section_title> List </section_title> <table> <cell> 4 <col_header> Rank </col_header> </cell> <cell> Maricopa <col_header> County </col_header> </cell> <cell> Arizona <col_header> State </col_header> </cell> </table>
The U.S. Census Bureau estimated Maricopa population was the fourth-most populous in the United States of Arizona.