Editors' Summary: Since the Supreme Court's decision in Rapanos v. United States, courts, practitioners, and scholars have continued to discuss the socalled Kennedy test and its significant nexus criterion. In this Article, authors William W. Sapp, Mina Makarious, and M. Allison Burdette explore the historic navigability test, one tool that can be used to establish a significant nexus to a traditional navigable water. The authors begin by providing a history of traditional navigable waters. They move on to discuss the Rapanos decision and, in particular, the important role played by traditional navigable waters in Justice Anthony M. Kennedy's significant nexus test. Then they discuss the three tests that have arisen in this country for determining whether a water is a traditional navigable water, elaborating on the historic navigability prong of the traditional navigability test. Finally, they discuss some key historic use cases to explain how this approach can be used to greatest effect.