There are 11 US Post Offices in Mcdonough County serving a total of 33,376 residents equating to 3,034 residents per post office. It's estimated that approximately 53,272 packages are handled across the 11 county post offices annually. McDonough County is a county located in the U.S. state of Illinois. According to the 2010 census, it had a population of 32,612. Its county seat is Macomb. The Macomb, IL Micropolitan Statistical Area includes all of McDonough County."