Yellowstone Lake is the largest lake in North America at this high an elevation, 7,733 feet. It is 20 miles long and 14 miles across from West Thumb to the opposite shore. It covers 132 square miles and has a shoreline of 114 miles. It has an average depth of 139 feet, although the deepest point is 410 feet. Islands in the lake are Dot Island, Frank Island, Stevenson Island, Molly Island (in the southeast arm), and Peale Island (in the south arm).