Allentown (Pennsylvania Dutch: Allenschteddel) is a city located in Lehigh County, Pennsylvania, United States. It is Pennsylvania's third most populous city and the 226th 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 all of 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 2010. It constitutes a portion of the New York City Metropolitan Area and is the county seat of Lehigh County. In 2012, the city celebrated the 250th anniversary of its founding in 1762.