Affectionately called the “Linchpin of the Great Lakes” by the United States Army Corps of Engineers, the Soo Locks are an engineering marvel with roots dating back to the mid-1800s. Each year it’s estimated that 500,000 people visit these iconic locks that connect Lakes Superior and Huron.

Thanks to the Soo Locks freighters over 1,000 feet in length can traverse freely along the St. Marys River all the way from Duluth, Minnesota outward into the Atlantic Ocean and beyond. Roughly 7,000 vessels pass through the Locks yearly hauling nearly 86 million tons of cargo. See how freighters, barges, tugboats and more are lifted and lowered the 21-foot difference between Superior and Huron here.

Most ships utilize the Poe Lock (1,200 feet) which was rebuilt in 1968 to accommodate larger and more modern ships. The MacArthur Lock (800 feet), constructed in 1943, is still in operation as well. It is the lock closest to Sault Ste. Marie, which the observation deck in the Soo Locks Park overlooks, and was named after General Douglas MacArthur. The Davis and Sabin Locks were built in 1914 and 1919 respectively. Currently, only the Poe and MacArthur Locks are in operation. Construction of a New Soo Lock is currently underway. The New Soo Lock will be the same size as the Poe Lock.

During the region’s earliest days, the Ojibway Indians who lived nearby portaged their canoes around the “Bawating” (rapids) to reach Lake Superior from the St. Marys River. When the settlement of the Northwest Territory brought increased trade and large boats it became necessary to unload the boats haul the cargoes around the rapids in wagons and reload in other boats.

In 1797, the Northwest Fur Company constructed a navigation lock 38 feet long on the Canadian side of the river for small boats. This lock remained in use until destroyed in the War of 1812. Freighters and boats were again portaged around the rapids. Congress passed an act in 1852 granting 750,000 acres of public land to the State of Michigan as compensation to the company that would build a lock permitting waterborne commerce between Lake Superior and the other Great Lakes. The Fairbanks Scale Company, which had extensive mining interests, in the upper peninsula, undertook this challenging construction project in 1853.

The State Lock was the first chamber built-in 1855. Thanks to the State Lock the 21-foot difference in water levels was tamed, and easy transport between the two Great Lakes became possible.