The Soo Locks are a set of parallel locks, operated and maintained by the U.S. Army Corps of Engineers, Detroit District, which enable ships to travel between Lake Superior and the lower Great Lakes. They are located on the St. Marys River between Lake Superior and Lake Huron, between the Upper Peninsula of the US state of Michigan and the Canadian province of Ontario. They bypass the rapids of the river, where the water falls. The locks pass an average of 10,000 ships per year, despite being closed during the winter from January through March, when ice shuts down shipping on the Great Lakes. The winter closure period is used to inspect and maintain the locks. The locks share a name with the two cities named Sault Ste. Marie, in Ontario and in Michigan, located on either side of the St. Marys River. The Sault Ste. Marie International Bridge between the United States and Canada permits vehicular traffic to pass over the locks. A railroad bridge crosses the St. Marys River just upstream of the highway bridge. The first locks were opened in 1855. Along with the Erie Canal, constructed in 1824 in central New York State, they were one of the great infrastructure engineering projects of the antebellum United States. The Soo Locks were designated a National Historic Landmark in 1966. During World War II, the Soo Locks and the St. Marys River waterway were heavily guarded by U.S. and Canadian forces coordinated by the U.S. Army's Central Defense Command. A one-way German air attack on the locks, based in Norway, was thought to be possible.
United States locks
The U.S. locks form part of a canal formally named the St. Marys Falls Canal. The entire canal, including the locks, is owned and maintained by the United States Army Corps of Engineers, which provides free passage. The first iteration of the U.S. Soo Locks was completed in May 1855; it was operated by the State of Michigan until transferred to the U.S. Army in 1881. The first federal lock, the Weitzel Lock, was built in 1881 and replaced by the MacArthur Lock in 1943. The current configuration consists of four parallel lock chambers, each running east to west. Starting at the Michigan shoreline and moving north toward Ontario, these are:
The MacArthur Lock, built in 1943. It is long, wide, and deep. This is large enough to handle ocean-going vessels that must also pass through the smaller locks in the Welland Canal. The first vessel through was the SS Carl D. Bradley.
The Poe Lock was completed on August 3, 1896. The first vessel to pass through was the U.S. Army Corps of Engineers tug USS Hancock. The original Poe Lock was engineered by Orlando Poe and, at long and wide, was the largest in the world when completed in 1896. The lock was re-built in 1968 to accommodate larger ships, after the Saint Lawrence Seaway opened and made passage of such ships possible to the Great Lakes. It is now long, wide, and deep. It can take ships carrying of cargo. The Poe is the only lock that can handle the large lake freighters used on the upper lakes. The first passage after the rebuild was by the Phillip R. Clarke in 1969.
The Davis Lock, built in 1914. It is long, wide, and deep. This lock is used less frequently to lock light freighters, tour boats, and small craft when traffic warrants. The SS James A Farrell was the first vessel to lock through.
The Sabin Lock, built in 1919. It is long, wide, and deep. This lock has been placed in caretaker status and is no longer used. To get the Sabin lock up and running again would cost roughly $5 million.
The Davis and Sabin locks have been slated for replacement since 1986 with a new 'Super-Lock', which would provide a second lock capable of accommodating the "lakers". Groundbreaking for the new lock project was held on June 30, 2009. This construction will further limit usage of the Davis Lock. Funding was approved October 23, 2018. North of the Sabin Lock is an additional channel with a small hydroelectric plant, which provides electricity for the lock complex.
Engineers Day
The U.S. Army Corps of Engineers, Detroit District, operates the Soo Locks Visitors Center and viewing deck for the public. On the last Friday of every June, the public is allowed to go behind the security fence and cross the lock gates of the U.S. Soo Locks for the annual Engineers Day Open House. During this event, visitors are able to get close enough to touch ships passing through the two regularly operating locks.
Canadian lock
A single small lock is operated on the Canadian side of the Soo. Opened in 1895, it was rebuilt in 1998 within a damaged older lock, a wall of which collapsed in 1987, and is long, wide and deep. The Canadian lock is used for recreational and tour boats; major shipping traffic uses the U.S. locks.
