There are 16 US Post Offices in Knox County serving a total of 52,869 residents equating to 3,304 residents per post office. It's estimated that approximately 84,385 packages are handled across the 16 county post offices annually. Knox County is a county located in the U.S. state of Illinois. According to the 2010 census, it had a population of 52,919. Its county seat is Galesburg. Knox County comprises the Galesburg, IL Micropolitan Statistical Area."