Bethlehem is a city in Northampton and Lehigh counties in the Lehigh Valley region of eastern Pennsylvania, United States. As of the 2020 census, Bethlehem had a total population of 75,781, making it the second-largest city in the Lehigh Valley after Allentown and the seventh-largest city in the state. Among its total population as of 2020, 55,639 were in Northampton County and 19,343 were in Lehigh County. The city is located along the Lehigh River, a 109-mile-long (175 km) tributary of the Delaware River.