Warren County is a county located in the U.S. state of New Jersey. According to the 2020 census, the county was the state's 19th-most populous county, with a population of 109,632, its highest decennial count ever and an increase of 940 (+0.9%) from the 2010 census count of 108,692, which in turn reflected an increase of 6,255 (+6.1%) from 102,437 counted at the 2000 census. The county is part of the North Jersey region of the state.

The Lehigh Valley is a geographic and metropolitan region formed by the Lehigh River in Lehigh and Northampton counties in eastern Pennsylvania. It is a component valley of the Great Appalachian Valley bounded to its north by Blue Mountain, to its south by South Mountain, to its west by Lebanon Valley, and to its east by the Delaware River and Warren County, New Jersey. The Lehigh Valley is about 40 miles (64 km) long and 20 miles (32 km) wide. The Lehigh Valley's largest city is Allentown, the third-largest city in Pennsylvania and the county seat of Lehigh County, with a population of 125,845 residents as of the 2020 census.