Madison County was formed on January 13, 1846. It has been self-governed since 1849. It was named after James Madison, the fourth President of the United States. Madison County is located in the U.S. state of Iowa. As of 2020 , the population is 16,548 ,. Its county seat is Winterset, and it is one of the five counties that make up the Des Moines-West Des Moines 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 book and movie, The Bridges of Madison County.