There are 5 US Post Offices in Butler County serving a total of 20,684 residents equating to 4,137 residents per post office. It's estimated that approximately 33,014 packages are handled across the 5 county post offices annually. Butler County is a county in the U.S. state of Alabama. As of the 2010 census, the population was 20,947. Its county seat is Greenville. Its name is in honor of Captain William Butler, who was born in Virginia and fought in the Creek War, and who was killed in May 1818.