There are 6 US Post Offices in Mississippi County serving a total of 14,853 residents equating to 2,476 residents per post office. It's estimated that approximately 23,707 packages are handled across the 6 county post offices annually. Mississippi County is a county located in the Bootheel of the U.S. state of Missouri, with its eastern border formed by the Mississippi River. As of the 2010 census, the population was 14,358. The largest city and county seat is Charleston. The county was officially organized on February 14, 1845, and was named after the Mississippi River."