The Great Lakes are a group of five freshwater lakes in North America. People have sailed on them since the 17th century, and many ships have been lost while traveling through them. Some of these ships were never found, so the exact number of shipwrecks in the lakes is unknown. The Great Lakes Shipwreck Museum estimates that about 6,000 ships and 30,000 people have been lost in the lakes. Historian and mariner Mark Thompson believes the actual number of shipwrecks is likely more than 25,000. Between 1816, when the ship Invincible sank, and 1975, when the Edmund Fitzgerald sank, the Whitefish Point area alone is believed to have caused the loss of at least 240 ships.