There are 14 US Post Offices in Logan County serving a total of 30,029 residents equating to 2,145 residents per post office. It's estimated that approximately 47,930 packages are handled across the 14 county post offices annually. Logan County is a county located in the U.S. state of Illinois. According to the 2010 census, it had a population of 30,305. Its county seat is Lincoln. Logan County comprises the Lincoln, IL Micropolitan Statistical Area, which is included in the Springfield-Jacksonville-Lincoln, IL Combined Statistical Area."