St. Marys River

About

St. Marys River, Michigan — 1855 Soo Locks, Sault Ste Marie, Ojibwe-Odawa. The gauge at the outlet reflects the river's outsized scale: USGS station 04127885 carries an average of roughly 75,400 cubic feet per second, the outflow of an entire Great Lake rather than a single stream. That volume is the same force that once frustrated navigators at the rapids and later powered the region's industry. Rated Class I, the St. Marys is a border water — the line between Michigan and Ontario — connecting Lake Superior to Lake Huron.

Long before the locks, the river was the homeland of the Anishinaabe (Ojibwe) and the site of the Sault, the rapids that gave Sault Ste. Marie its name. For centuries it served as a primary gathering place, fishing ground, and trade center. The 1795 Treaty of Greenville and the 1820 Treaty of Sault Ste. Marie established the framework for later land cessions, and the Sault Ste. Marie Tribe of Chippewa Indians maintains cultural connections and treaty-protected rights to the watershed today, alongside the historic Three Fires Council.

The river's defining moment came with the 1855 completion of the State Locks, a predecessor of today's Soo Locks system that opened the Upper Great Lakes to commercial navigation. Operated by the U.S. Army Corps of Engineers since 1855, the St. Marys Falls Ship Canal knitted Lake Superior into the commerce of the lower lakes. Construction continued for decades: the Weitzel Lock rose between 1881 and 1896, and the Poe Lock was reconstructed between 1908 and 1914. The 1914 American lock and the 1917 Canadian lock followed, with the second Poe Lock built from 1959 to 1963 and the MacArthur Lock modernized between 1968 and 1985.

The surrounding watershed carried its own industrial weight. From the 1840s through the 1920s, the St. Marys River watershed was logged to supply the Sault Ste. Marie sawmill industry that ran from roughly 1850 to 1910, the Algoma Steel operations of 1860–1910, and the Lake Superior lumber schooner trade of 1865–1920s. The white-pine stands were largely exhausted by 1910, and state forestry conservation began in 1915. The river's industrial character deepened at the turn of the century when construction of the Saint Marys Falls Hydropower Plant — the Edison Sault Power Plant — began in 1898 and the station opened in 1902, drawing power from the same descending water.

Recognition of that role arrived in 1966, when the Soo Locks Historic District was designated a National Historic Landmark. Modernization continues: the 2015 Soo Locks Upgrade Project, a $922 million federal investment, is building a second Poe-sized lock, the New Lock at the Soo, to secure reliable iron ore shipping. The 2010 Great Lakes Restoration Initiative has funded St. Marys River Area of Concern cleanup, including the remediation of 1.5 million cubic yards of contaminated sediment, and Sault Tribe water-quality monitoring ran from 2019 to 2024. In 2024 the Soo Locks marked their 100th anniversary. The river now supports more than 5,000 ship transits annually, moving 75 million tons of cargo, and paddlers know it through the St. Marys River Island Explorer Water Trail and the Whitefish Bay fishery.