The Soo Locks system, a National Historic Landmark on the St. Mary’s River at Sault Ste. Marie, Mich., is the only water passage between Lake Superior and the other Great Lakes.

Here are some facts about the Soo Locks System:

  • Two operating locks are the current 1,200'x110' Poe Lock, opened 1969 — the only one that can handle the lakes’ largest vessels, and the 800'x80' MacArthur Lock, opened in 1943. A new Poe-size lock will be on the site of two locks no longer used commercially — the Davis, built in 1914, and Sabin, built in 1919.
  • The Poe handles 91.7% of all Soo tonnage. Cargo includes iron ore, which accounts for nearly two-thirds of the total and is critical to steel mills on the lower lakes, as well as coal, grain and aggregates.
  • In 2021, 8,265 vessels with 72 million tons of cargo locked through compared to 5,982 with 60 million tons in Covid-impacted 2020.
  • Water level in Lake Superior is 21’ higher than Lake Huron.