There are 19 US Post Offices in Harford County serving a total of 211,039 residents equating to 11,107 residents per post office. It's estimated that approximately 336,842 packages are handled across the 19 county post offices annually. Harford County is a county in the U.S. state of Maryland. As of the 2010 census, the population was 244,826. Its county seat is Bel Air. Harford County is included in the Baltimore-Columbia-Towson, MD Metropolitan Statistical Area, which is also included in the Washington-Baltimore-Arlington, DC-MD-VA-WV-PA Combined Statistical Area."