There are 23 US Post Offices in Montgomery County serving a total of 396,384 residents equating to 17,234 residents per post office. It's estimated that approximately 632,673 packages are handled across the 23 county post offices annually. Montgomery County is a county located in the U.S. state of Ohio. As of the 2010 census, the population was 535,153, making it the fifth-most populous county in Ohio. The county seat is Dayton. The county was named in honor of Richard Montgomery, an American Revolutionary War general killed in 1775 while attempting to capture Quebec City, Canada. Montgomery County is part of the Dayton, Ohio Metropolitan Statistical Area."