There are 6 US Post Offices in Lawrence County serving a total of 17,533 residents equating to 2,922 residents per post office. It's estimated that approximately 27,985 packages are handled across the 6 county post offices annually. Lawrence County is a county located in the U.S. state of Mississippi. As of the 2010 census, the population was 12,929. Its county seat is Monticello. The county is named for the naval hero James Lawrence."