There are 4 US Post Offices in Lawrence County serving a total of 16,679 residents equating to 4,170 residents per post office. It's estimated that approximately 26,622 packages are handled across the 4 county post offices annually. Lawrence County is the easternmost county in the U.S. state of Illinois (excluding water boundaries). According to the 2010 census, it has a population of 16,833. Its county seat is Lawrenceville."