There are 13 US Post Offices in Hancock County serving a total of 18,226 residents equating to 1,402 residents per post office. It's estimated that approximately 29,091 packages are handled across the 13 county post offices annually. Hancock County is a county located in the U.S. state of Illinois. According to the 2010 census, it has a population of 19,104. Its county seat is Carthage, and its largest city is Hamilton. The county is made up of rural towns with many farmers. Hancock County is included in the Fort Madison-Keokuk, IA-IL-MO Micropolitan Statistical Area."