There are 12 US Post Offices in Putnam County serving a total of 35,821 residents equating to 2,985 residents per post office. It's estimated that approximately 57,174 packages are handled across the 12 county post offices annually. Putnam County is a county located in the U.S. state of Ohio. As of the 2010 census, the population was 34,499. Its county seat is Ottawa. The county was created in 1820 and later organized in 1834. Its 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."