The Susquehanna River could only cut through these ridges of the Appalachian mountains if it once flowed on a gently sloping landscape and has now cut down into a land with different kinds of rocks.

The Delaware Water Gap is a famous gap cut by the Delaware through the Appalachian Mountains. It was a vital route for early settlers moving west as it saved a difficult mountain journey.The Delaware Water Gap seen from Kittatinny Point in Delaware Water Gap National Recreational Area, New Jersey. The Delaware Water Gap is about 300 meters across at river level and 1,400 meters wide at the top. The river through the gap is 283 feet above sea level. The ridge of the Appalachians that the Delaware crosses is called the Blue Mountains in Pennsylvania and the Kittatinny Ridge in New Jersey. This is the first major ridge of the Appalachian mountains. The New Jersey mountain is Mount Tammany, named after the Native American Chief Tamanend. The Pennsylvania mountain is Mount Minsi, named after the Native American tribe of the area. The summit of Tammany is 1,540 ft (470 m) above sea level.

Antecedent drainage is common on most continents and it has played a major role in influencing the routes connecting cities.

The gaps that rivers seem to cut across mountains and upland ridges are often produced by antecedent rivers. Thus the gaps used by rivers in the rim of the London Basin and the Paris Basin are antecedent rivers, as are those that cut in to the Appalachian mountains of North America, most spectacularly, the Delaware and Cumberland Gaps.

Goosenecks State Park in Arizona is a dramatic example of a river cutting down as the land around it rose.