[1] The river is 70.8 miles (113.9 km) long measured from its source in Maheu Lake in Pine County, and 34.9 miles (56.2 km) from its confluence with the South Fork in Carlton County just east of the Minnesota-Wisconsin border.

[2] The Nemadji River empties into Lake Superior in an industrial neighborhood at Allouez Bay in the city of Superior's east-side neighborhood of Allouez and Wisconsin Point.

Most of the rivers' length flows in Douglas County, Wisconsin, entering near Foxboro and exiting in East End, Superior, near Loons Foot Boat Landing, USH 2/53, and the BNSF Taconite Plant Nemadji comes from the Ojibwe language, "ne-madji-tic-guay-och" (Nemanjitigweyaag in the current spelling), meaning "left river,"[3][4] opposed to the Saint Louis River, which when viewed from Allouez Bay is the "right river."

In the 1992 Nemadji River train derailment a Burlington Northern train derailed south of Superior, releasing nearly 22,000 gallons of aromatic hydrocarbons including liquid benzene, a highly toxic chemical, into the Nemadji River.

Fish and Wildlife Service proposed a draft that would use funds received from a settlement with Burlington Northern to restore a portion of the Lake Superior basin affected by the incident.