There are 8 US Post Offices in Clay County serving a total of 21,540 residents equating to 2,693 residents per post office. It's estimated that approximately 34,380 packages are handled across the 8 county post offices annually. Clay County is a county located in the U.S. state of Kentucky. As of the 2010 census, the population was 21,730. Its county seat is Manchester. The county was formed in 1807 and named in honor of Green Clay (1757\u20131826). Clay was a member of the Virginia and Kentucky State legislatures, first cousin once removed of Henry Clay, U.S. Senator from Kentucky and Secretary of State in the 19th century."