The St. Louis River is the largest tributary feeding Lake Superior. For centuries, the river has been of cultural and economic significance to the people living along its banks. The Duluth-Superior Harbor, which sits at the confluence of the St. Louis River and Lake Superior, was an appealing location for large-scale maritime and industrial activities, beginning in the late 19th century.
The area's industrial heritage includes a legacy of sediment contamination—decades-old deposits of chemicals and heavy metals that remain in the riverbed. Many areas of the harbor still contain concentrations regarded as harmful to human well-being and the health of the ecosystem. Through the St. Louis River Area of Concern Remedial Action Plan, several sites have been targeted for cleanup and restoration. Among these are Slip 3 and Slip C, man-made slips which have been altered and used by multiple industries since their construction more than a century ago.