This postcard depicts the Davis Lock, which is described as the longest lock in the world. The lock is 1350 feet long and 80 feet wide. The view was taken from he bow of a boat entering the lock. There is also a bi-plane flying overhead. This card is unused, but it does have several numbers written on the back, which I believe are inventory numbers for the former owner's collection.
This card was published exclusively for A. E. Young, Saul Ste. Marie, Michigan. It is in excellent condition.
Postcard of the Longest Lock in the World, The Davis Lock in Michigan