At an elevation of 7,733 feet (2357 m) above sea level, Yellowstone Lake is the largest high elevation lake (above 7,000 feet) in North America. It has an average depth of 139 feet (42 m), and its greatest depth is 410 feet (131 m). It is 20 miles in length and 14 miles wide. It covers 132 square miles and has 141 miles of shoreline. Yellowstone Lake has the largest population of cutthroat trout in North America. Unfortunately, the lake trout that were illegally introduced into the lake, sometime in the 1980’s pose a serious threat to the native cutthroat trout. Currently, only 1/10th of the cutthroat population that once existed in the lake is found there.