There are 10 US Post Offices in Harrison County serving a total of 163,889 residents equating to 16,389 residents per post office. It's estimated that approximately 261,585 packages are handled across the 10 county post offices annually. Harrison County is a county located in the U.S. state of Mississippi. As of the 2010 census, the population was 187,105, making it the second-most populous county in Mississippi. Its county seats are Biloxi and Gulfport. The county is named after U.S. President William Henry Harrison. Harrison County is part of the Gulfport-Biloxi-Pascagoula, MS Metropolitan Statistical Area. The county was severely damaged from both Hurricane Camille on August 17, 1969 and Hurricane Katrina on August 29, 2005, causing catastrophic effects."