There are 25 US Post Offices in Lehigh County serving a total of 214,448 residents equating to 8,578 residents per post office. It's estimated that approximately 342,283 packages are handled across the 25 county post offices annually. Lehigh County is a county located in the Lehigh Valley region of the U.S. state of Pennsylvania. As of the 2010 census, the population was 349,497. Its county seat is Allentown, the state's third largest city behind Philadelphia and Pittsburgh. The county, which was first settled around 1730, was formed in 1812 with the division of Northampton County into two counties. It is named after the Lehigh River, whose name is derived from the Delaware Indian term Lechauweki or Lechauwekink, meaning \"where there are forks\". Lehigh County is included in the Allentown-Bethlehem-Easton, PA-NJ Metropolitan Statistical Area, which is also included in the New York City-Newark, New Jersey, NY-NJ-CT-PA Combined Statistical Area. It is currently the fastest growing county in Pennsylvania and among the fastest growing nationwide, ranking in the 79th percentile overall for the 2010 to 2012 time period."