Cape Cod Canal, Massachusetts

At 17.4 miles long and 480 feet wide, the Cape Cod Canal has been called the widest sea-level canal in the world. Construction started in 1909, and finished in 1914, and its width was almost doubled in the 1930's. The Canal transformed Cape Cod from a peninsula to an island, and lessened travel time for coastal shipping, which no longer needed to traverse the dangerous waters around the Cape.