There are 7 US Post Offices in Putnam County serving a total of 35,542 residents equating to 5,077 residents per post office. It's estimated that approximately 56,729 packages are handled across the 7 county post offices annually. Putnam County is a county located in the U.S. state of Indiana. As of 2010, the population was 37,963. The county seat is Greencastle. The name is in honor of Israel Putnam, who was a hero in the French and Indian War and a general in the American Revolutionary War. The county was formed on April 1, 1822 from Owen and Vigo Counties and parts of the Wabash New Purchase attached to Monroe and Parke Counties. Putnam County is included in the Indianapolis-Carmel-Anderson, IN Metropolitan Statistical Area."