Putnam County is a county located in the U.S. state of Indiana. As of the 2010 United States Census, the population was 37,963. The county seat is Greencastle. The county was named for Israel Putnam, a hero in the French and Indian War and a general in the American Revolutionary War. The county was created in 1821 and organized in April 1822. Putnam County is included in the Indianapolis-Carmel-Anderson, IN Metropolitan Statistical Area.