There are 3 US Post Offices in Mercer County serving a total of 21,988 residents equating to 7,329 residents per post office. It's estimated that approximately 35,095 packages are handled across the 3 county post offices annually. Mercer County is a county located in the U.S. state of Kentucky. As of the 2010 census, the population was 21,331. Its county seat is Harrodsburg. The county was formed from Lincoln County in 1785 and is named for Revolutionary War General Hugh Mercer, who was killed at the Battle of Princeton in 1777. It is a prohibition or dry county, though Harrodsburg and Pleasant Hill allow the sale of alcohol by the drink. In Kentucky, and perhaps elsewhere, this is referred to as being a \"moist\" county - wet sells package liquor, wine and beer, dry sells no alcoholic beverages (legally), \"moist\" serves by the drink, primarily in restaurants. Boyle County (Danville) immediately to the south along US Hwy 127, is fully wet, and has two large liquor outlet stores, plus several smaller, privately owned ones."