There are 9 US Post Offices in Morgan County serving a total of 35,451 residents equating to 3,939 residents per post office. It's estimated that approximately 56,584 packages are handled across the 9 county post offices annually. Morgan County is a county located in the U.S. state of Illinois. According to the 2010 census, it had a population of 35,547. Its county seat is Jacksonville. Morgan County is part of the Jacksonville, IL Micropolitan Statistical Area, which is also included in the Springfield-Jacksonville-Lincoln, IL Combined Statistical Area."