The BBC rates Crater Lake in Oregon as the cleanest in the United States, and one of the cleanest in the world. The United States Environmental Protection Agency considers Lake Tahoe one of the cleanest lakes in the country, and MSN states that Lake Coeur d'Alene in Idaho also tops the list.
Crater Later in Oregon lies in the crater of the ancient volcano Mount Mazama and reaches nearly 2,000 feet deep. Part of its pristine clarity comes from the fact it is fed only by rain and snow and remains uncontaminated by streams and rivers. Its deep blue color is proof of its cleanness; clean water doesn't absorb blue wavelengths of visible light.
Lake Tahoe is also considered one of the cleanest lakes as evidenced by its clarity and dark blue color. This lake is nearly 2 million years old and covers almost 200 square miles, reaching to depths of 1,600 feet.
MSN touts Lake Coeur d'Alene in Idaho as another of the cleanest, clearest lakes, calling it a national treasure. This lake rests in a basin carved by an ancient glacier. Not only is the lake considered beautiful, but it is rife with recreational fun, from boating and fishing to golfing.