The Delaware Water Gap is a water gap on the border of the U.S. states of New Jersey and Pennsylvania where the Delaware River cuts through a large ridge of the Appalachian Mountains. The gap makes up the southern portion of the Delaware Water Gap National Recreation Area, which is used primarily for recreational purposes, such as canoeing, fishing, hi…The Delaware Water Gap is a water gap on the border of the U.S. states of New Jersey and Pennsylvania where the Delaware River cuts through a large ridge of the Appalachian Mountains. The gap makes up the southern portion of the Delaware Water Gap National Recreation Area, which is used primarily for recreational purposes, such as canoeing, fishing, hiking, and rock climbing. Though the US National Park Service manages the National Recreation Area, portions of the water gap are also patrolled by New Jersey Division of Parks and Forestry.