The Lehigh Valley, also known as the Allentown-Bethlehem-Easton, PA-NJ metropolitan area and referred to locally as The Valley, is an official metropolitan region consisting of Lehigh, Northampton and Carbon counties in eastern Pennsylvania and Warren county on the western edge of New Jersey, in the United States. The Lehigh Valley is the third most populous region of Pennsylvania, following metropolitan Philadelphia and Pittsburgh. The region is named for the Lehigh River, which runs through it. It is part of the Great Appalachian Valley.