There are 12 US Post Offices in Eaton County serving a total of 147,814 residents equating to 12,318 residents per post office. It's estimated that approximately 235,928 packages are handled across the 12 county post offices annually. Eaton County is a county in the U.S. state of Michigan. As of the 2010 census, the population was 107,759. The county seat is Charlotte. The county was organized in 1837 and named for John Eaton, who was Secretary of War under U.S. President Andrew Jackson, making it one of Michigan's Cabinet counties. Eaton County is included in the Lansing-East Lansing, MI Metropolitan Statistical area in Central Michigan."