Soo Locks, Ship lock system in Sault Ste. Marie, United States

The Soo Locks form a system of parallel canals with chambers that adjust the elevation difference between Lake Superior and Lake Huron along the St. Marys River. The installation includes four lock chambers of varying size, handling cargo vessels, bulk carriers, and occasional passenger ships at the same time.

Construction of the first lock began in 1855 to allow ships to bypass the natural waterfall at St. Marys Rapids. The system expanded over the decades to accommodate larger vessels, and received National Historic Landmark designation in 1966.

The observation platform above the chambers shows the daily work of lock operators and the passage of massive cargo ships. Visitors follow the entire process, from ships entering to the slow rise or fall of water level, while engines and cables work beneath their feet.

The facility operates from March through January, as long as navigation on the Great Lakes remains possible. A free viewing platform offers direct views of ship passages, and short walkways connect visitors to the different chambers.

The MacArthur Lock, one of the four chambers, can accommodate ships up to 800 feet (240 meters) long, making it one of the largest inland locks in North America. During the season, several freighters pass daily, often loaded with iron ore or grain from the Upper Midwest.