Mississagi was a Type L6-S-B1 lake freighter launched in 1943. Originally she was powered by a 2,500 horsepower (1,900 kW) triple-expansion steam engine. In 1985 her steam engines were replaced by a 4,500 horsepower (3,400 kW) diesel engine. She was built to a design from the United States Maritime Commission by the Great Lakes Engineering Works in River Rouge, Michigan. She had fifteen sister ships, also built to the Maritime Commission's design, known colloquially as "Maritimers".