There are 3 US Post Offices in Forrest County serving a total of 66,506 residents equating to 22,169 residents per post office. It's estimated that approximately 106,151 packages are handled across the 3 county post offices annually. Forrest County is a county located in the U.S. state of Mississippi. As of the 2010 census, the population was 74,934. Its county seat and largest city is Hattiesburg. The county was created from Perry County in 1908 and named in honor of Nathan B. Forrest, a Confederate general in the American Civil War. Forrest County is part of the Hattiesburg, MS Metropolitan Statistical Area."