The Soo Locks were built to help ships traverse the height difference of 25 feet between Lakes Superior and Huron. Built in the St. Mary’s River that connects these to great bodies of water, the locks have evolved over the years. Generally, they have gotten bigger over time. The locks are in the midst of building a new even larger lock, by taking the space currently occupied by two older and smaller locks. This post’s photo is of this year’s poster for the locks. It is reminiscent of the 1930s posters that the National Park Service had made. of My only complaint about it is that none of the freighters have yellow hulls. Most are red, a few are grey, but none are yellow.