Lehigh County is a county located in the Lehigh Valley region of the eastern part of the U.S. state of Pennsylvania. As of the 2000 U.S. Census, the county's population was 312,090. Its county seat is Allentown, the state's third largest city behind Philadelphia and Pittsburgh. In addition to Allentown, the county includes the western section of the city of Bethlehem, six boroughs and 14 townships.
The county, which was first settled around 1730, was formed in 1812 with the division of Northampton County into two counties. It is named after the Lehigh River, whose name is derived from the Delaware Indian term Lechauweki or Lechauwekink, meaning "where there are forks"..