Wetlands are vital to the health of the nation’s waterways. Even small, geographically isolated wetlands can perform important functions that benefit their surrounding ecosystem. Despite the important role of smaller wetlands, the federal Clean Water Act (CWA) protection of these areas is limited to those wetlands that satisfy legal tests limited by the Commerce Clause of the Constitution. The main test to establish jurisdiction—the “significant nexus” test—relies on a connection between a wetland and a navigable-in-fact waterway. Smaller wetlands, however, may not each have individual connections that are sufficient to satisfy the significant nexus test. When wetlands are “similarly situated,” therefore, the individual effects of each wetland may be aggregated to assess the connection to a navigable-in-fact waterway. This Note proposes that the hydrogeomorphic (HGM) classification system, which is already used to assess wetland functions and values, be used to establish when wetlands are similarly situated. Using HGM classification this way is consistent with the legislative purpose of the CWA and Supreme Court precedent in United States v. Rapanos, would improve the efficiency of CWA jurisdictional determinations, and would allow small, geographically isolated wetlands to fall under the CWA’s protections.