Allentown is a city in Lehigh County, Pennsylvania. It is Pennsylvania's thirdmostpopulous city and the 233rdlargest city in the United States. As of the 2010 census, the city had a total population of 118,032. As of 2019, it is the fastest growing major city in Pennsylvania with an estimated 121,442 residents. It is the county seat of Lehigh County and the largest city in the metropolitan area known as the Lehigh Valley. The city, founded in 1762, celebrated its 250th anniversary in 2012. Located on the Lehigh River, Allentown is the largest of three adjacent cities (Allentown, Bethlehem, and Easton) in Northampton and Lehigh counties that make up the Lehigh Valley region of eastern Pennsylvania. Allentown is approximately 55 miles north of Philadelphia, 75 miles south of Scranton and the Wyoming Valley, 80 miles east of Harrisburg, and 85 miles west of New York City.