The Clean Water Act (CWA) is the primary federal mechanism by which the physical, chemical, and biological integrity of streams, lakes, and wetlands are protected in the U.S. The CWA has evolved considerably since its initial passage in 1948, including explicit expansions and contractions of jurisdictional scope through a series of legislative actions, court decisions, and agency rules. Here, we provide a practical summary of the CWA’s evolution, detailing the major updates or revisions and their circumstances. Additionally, we identify the jurisdictional scope of the law for rivers, lakes, and wetlands based on the language used and implementation by the agencies during the same time period. While the rulemaking process does not commonly include a translation of language to on-the-ground implications, quantifying the (un)certainties and magnitude of changes is an important perspective to understanding the implications of environmental regulation development, litigation, and enforcement. Thus, we translate the enforcement norms and definitions into quantitative estimates for water bodies in the Wabash River Basin as a demonstration of the spatial realization of changing environmental regulations.