Why Isn’t Lake St. Clair a great lake?

Why Isn’t Lake St. Clair Considered a Great Lake?

Lake St. Clair plays a vital role in the Great Lakes water system. Located between Lake Huron and Lake Erie, it connects the two via the St. Clair River and Detroit River. Despite its ecological significance, recreational popularity, and economic importance, Lake St. Clair is not officially designated as one of the Great Lakes. This often raises the question: Why isn’t Lake St. Clair considered a Great Lake? The answer lies in a combination of geographic, hydrologic, historical, and legal factors.

1. Size Matters: It's Simply Smaller

The most straightforward reason Lake St. Clair is not a Great Lake is its size. The five officially recognized Great Lakes—Superior, Michigan, Huron, Erie, and Ontario—are among the largest freshwater lakes in the world by surface area and volume. Lake St. Clair, by comparison, is considerably smaller:

• Surface area: ~430 square miles (1,114 km²)
• Average depth: ~11 feet (3.4 meters)
• Maximum depth: ~27 feet (8.2 meters)

Compare this to Lake Ontario, the smallest of the Great Lakes, which is over 7,300 square miles in surface area and 802 feet deep at its deepest point. Lake St. Clair is shallower and more river-like in hydrology, acting more as a connecting channel than an expansive inland sea.

2. Geographic and Hydrological Function

Although it is a distinct body of water, Lake St. Clair functions as part of the Great Lakes connecting channel system. It receives water from Lake Huron via the St. Clair River and flows into Lake Erie through the Detroit River. This places it within the Great Lakes Basin, but not as a standalone Great Lake.

In hydrological terms, Lake St. Clair is considered an interlake waterway or lake in a river system, rather than one of the primary lakes in the chain. The U.S. Army Corps of Engineers and other scientific and environmental agencies categorize it as a connecting lake, similar to the Niagara River or St. Marys River, not as a Great Lake in its own right.

3. Historical and Legal Definitions

When the Great Lakes were formally named and classified, Lake St. Clair was not included in the original list. The concept of “The Great Lakes” became widely recognized in the 19th and early 20th centuries, primarily for navigation, commerce, and political reasons. The five Great Lakes were named for their immense size and global significance as freshwater reserves.

In legal and administrative terms, especially in federal and state legislation, “The Great Lakes” refers only to the five major lakes. This impacts environmental policy, trade law, and education. For instance, the Great Lakes Compact, a U.S. interstate agreement signed in 2008 to regulate water use, includes the five Great Lakes and their direct tributaries—but not Lake St. Clair as an independent Great Lake.

4. Ecological and Economic Importance – Despite the Exclusion

Despite not being officially a Great Lake, Lake St. Clair is ecologically and economically vital:

• It is one of the best sport fishing lakes in North America, especially for muskellunge and smallmouth bass.
• Its wetlands, especially the St. Clair Flats, form one of the largest freshwater delta systems in the world.
• The lake supports shipping and boating traffic as part of the Great Lakes–St. Lawrence Seaway.
• It provides drinking water to communities on both the U.S. and Canadian sides.

Many experts argue that Lake St. Clair deserves “unofficial Great Lake” status because of these factors.

5. Efforts to Reclassify or Raise Awareness

There have been occasional efforts to gain recognition for Lake St. Clair as a “sixth Great Lake.” In fact, in 1998, a Michigan lawmaker proposed legislation to have Lake St. Clair officially designated as a Great Lake for educational purposes. While the resolution passed in Michigan, it had no effect on federal or international recognition.

However, some scientific studies, local educational initiatives, and conservation campaigns do refer to Lake St. Clair as the “forgotten Great Lake” to highlight its importance and the need for environmental protection.

Conclusion

Lake St. Clair is not classified as a Great Lake due to its smaller size, role as a connecting body, and historic legal definitions. Nonetheless, it plays an essential part in the Great Lakes ecosystem, supports thriving wildlife and recreation, and serves as a key hub for waterborne trade and transportation. While it may never receive the official title of “Great Lake,” its value is no less significant, and it continues to be cherished by those who live near it and visit its shores.