There are 6 US Post Offices in Madison County serving a total of 16,833 residents equating to 2,806 residents per post office. It's estimated that approximately 26,867 packages are handled across the 6 county post offices annually. Madison County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 15,679. The county seat is Winterset. Madison County is included in the Des Moines\u2013West Des Moines, IA Metropolitan Statistical Area. Madison County is famous for being the county where John Wayne was born, and for a number of covered bridges. These bridges were featured in the 1992 book, 1995 movie, and 2014 musical The Bridges of Madison County."