The diversity of the Delaware River watershed, and the human settlement patterns within it, is due to geology and topography. The 41 miles of the Delaware National Scenic River lie within the boundaries of the Delaware Water Gap National Recreation Area. This portion of the river was designated Wild and Scenic in 1978 and is famous for its folded mountains and water gaps.

As the Deleware River leaves the Appalachian Plateau at Port Jervis, New York, the slope of the river flattens somewhat and increases its meander pattern. In this 40 mile reach through the Ridge and Valley Province, the river is confined in a narrow valley surrounded by high hills and mountains.

Numerous islands exist in this reach and many tributaries enter the Delaware River after tumbling over beautiful, multi-stepped waterfalls. Most of this section of river is contained in the Delaware Water Gap National Recreation Area, a 70,000 acre area managed by the National Park Service. With over 4 million visitors per year, the recreation area is the 10th busiest unit in the National Park System. River recreation includes fishing, boating, canoeing and swimming at two major beaches maintained by the National Park Service. This reach of the Delaware River has also been added to the National Wild and Scenic Rivers System as the Middle Delaware Scenic and Recreational River.

The Delaware River breaks out of the Ridge and Valley Province in dramatic fashion. The Delaware Water Gap was created when the proto-Appalachian Mountains were formed. Being older than the mountains, the Delaware River cut its gap as the mountains rose. During the heyday of Victorian resort hotels, the Water Gap was promoted as the World's Eighth Scenic Wonder. The Appalachian Trail crosses the Delaware River in the Gap.