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–West 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.