
The southernmost lock & dam on the Mississippi River, and the only one south of the confluence of the Mississippi and Missouri rivers, Lock & Dam 27 moves more cargo than any other lock and dam on the Mississippi. It was built in response to a "chain of rocks" that made the river unnavigable in low water. The lock and dam are unique on the Mississippi, because the dam is a rock weir and the lock isn't connected to the dam and is actually 3 miles away at the southern end of the Chain of Rocks Canal which allows traffic to bypass the unnavigable portion.