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. Bethlehem lies in the geographic center of the Lehigh Valley, a metropolitan region of 731 sq mi (1,890 km2) with a population of 861,899 people as of the 2020 census that is Pennsylvania's third-most populous metropolitan area and the 68th-most populated metropolitan area in the U.S. Bethlehem borders Allentown to its west and is 48 miles (77 km) north of Philadelphia and 72 miles (116 km) west of New York City. There are four sections to the city: central Bethlehem, the south side, the east side, and the west side. Each of these sections blossomed at different times in the city's development and each contains areas recognized under the National Register of Historic Places. Norfolk Southern Railway's Lehigh Line, formerly the main line of the Lehigh Valley Railroad, runs through Bethlehem heading east to Easton and across the Delaware River to Phillipsburg, New Jersey. The Norfolk Southern Railway's Reading Line runs through Bethlehem and west to Allentown and Reading. Bethlehem has a long historical relationship with the celebration of Christmas. The city was christened as Bethlehem on Christmas Eve 1741 by Nicolaus Zinzendorf, a Moravian bishop. In 1747, Bethlehem was the first U.S. city to feature a decorated Christmas tree. On December 7, 1937, at a grand ceremony during the Great Depression, the city adopted the nickname Christmas City USA in a large ceremony. It is one of several Lehigh Valley locations, including Egypt, Emmaus, Jordan Creek, and Nazareth, whose names were inspired by locations in the Bible.