People visit Lake Superior to feel the power of nature or the peace of a quiet walk on the beach. But Lake Superior was once a battleground. The fight ultimately changed the way U.S. industry approaches the environment. Reserve Mining Company used to dump its waste rock into the lake. Tons of sediment poured into the lake every day. Lake Superior's water is famous for being clear and clean. But for 25 years, the waste rock turned the water gray-green and muddy. Duluth's drinking water, 50 miles away, was contaminated with a fiber that might cause cancer. The fight to stop the pollution was an early chapter in the history of the environmental movement. It established the principle that the government can force industry to clean up its pollution.