Which river forms the border between Delaware and New Jersey?

The river that forms the border between Delaware and New Jersey is the Delaware River. It serves as a natural boundary between the two states, flowing from north to south. The Delaware River plays a significant role in the geography and history of the region, being a vital waterway for transportation and trade. It is one of the major rivers in the northeastern United States and is well-known for its scenic beauty and recreational activities such as fishing, boating, and hiking along its banks.

In contrast, the Susquehanna River, while significant, primarily runs through Pennsylvania and Maryland and does not mark the border between Delaware and New Jersey. The Potomac River is located further south, separating Virginia and Maryland, and the Ohio River is even farther west, acting as a boundary between states such as Ohio and West Virginia. Thus, the Delaware River is the clear and correct answer as it directly defines the border in question.