Allentown, PA, United States (Pennsylvania Dutch: Allenschteddel) is a city located in Lehigh County, Pennsylvania, United States. It is Pennsylvania’s third most populous city, after Philadelphia and Pittsburgh, and the 224th largest city in the United States. As of the 2010 census, the city had a total population of 118,032 and is currently the fastest growing city in Pennsylvania. It is the largest city in the metropolitan area known as the Lehigh Valley, which had a population of 821,623 residents as of the 2010 U.S. Census and which constitutes a portion of the New York City Metropolitan Area. Allentown is the county seat of Lehigh County.In 2012, the city celebrated the 250th anniversary of its founding in 1762.