There are 8 US Post Offices in Effingham County serving a total of 35,144 residents equating to 4,393 residents per post office. It's estimated that approximately 56,094 packages are handled across the 8 county post offices annually. Effingham County is a county located in the U.S. state of Illinois. As of the 2010 census, the population was 34,242. Its county seat is Effingham. Effingham County comprises the Effingham, IL Micropolitan Statistical Area."