The Cadillac Canal runs between Cadillac Lake and Mitchell Lake. During logging days these lakes were known as Big and Little Clam Lakes and a historic marker near the east end details the canal's history.
The oddity here is in the fact that in the winter the canal freezes first, but once the lakes freeze, the canal opens for the rest of the winter. The canal freezes first, and is frozen for a short period of time, then once the lakes become cold enough to freeze, they are all frozen for a really short period of time, then the canal opens back up for the rest of the winter. Ripley's Believe it or Not could not figure out why it happens. The locals say that it's because the lakes are so different in depth and shape that the water flowing between the lakes opens the canal back up... but scientists have not confirmed this.