There are 23 US Post Offices in Armstrong County serving a total of 52,572 residents equating to 2,286 residents per post office. It's estimated that approximately 83,911 packages are handled across the 23 county post offices annually. Armstrong County is a county located in the U.S. state of Pennsylvania. As of the 2010 census, the population was 68,941. The county seat is Kittanning. The county was organized on March 12, 1800, from parts of Allegheny, Westmoreland and Lycoming Counties. It was named in honor of John Armstrong, who represented Pennsylvania in the Continental Congress and served as a major general during the Revolutionary War. Armstrong County is included in the Pittsburgh, PA Metropolitan Statistical Area."