The northwesternmost portion of the border follows a line from Lac Vieux Desert to the headwaters of the Montreal River. An 1847 survey established the east branch of the Montreal River as the border. However, the 1908 revision of the Constitution of Michigan specified that the west branch of the Montreal River was the proper border, which would have placed an additional 360 square miles of land on the Michigan side of the border. A 1926 Supreme Court decision awarded this tract of land to Wisconsin. Geography The Upper Peninsula contains , about 29 percent of the land area of the state (exclusive of territorial waters, which constitute about 40% of Michigan's total jurisdictional area). It is bounded on the north by Lake Superior, on the east by St. Marys River, on the south by Lake Michigan and Lake Huron, and on the west by Wisconsin and (counting the water border on Lake Superior) by Minnesota. It has about of continuous shoreline with the Great Lakes. There are about 4,300 inland lakes, the largest of which is Lake Gogebic, and of streams. Michigan's Upper Peninsula is bounded on land by Wisconsin to the southwest and west; and in territorial waters by Minnesota to the west, Ontario to the west, north and east, and the Door Peninsula of Wisconsin extends into Lake Michigan east of the western Upper Peninsula. Five Michigan Upper Peninsula counties include nearby major islands: Mackinac Island, Round Island and Bois Blanc Island in Lake Huron are in Mackinac County; Sugar Island and Neebish Island in the St. Marys River, and Drummond Island in Lake Huron are in Chippewa County; Grand Island is in Alger County; Summer Island is Delta County; and Isle Royale is part of Keweenaw County.The peninsula is divided between the flat, swampy areas in the east, part of the Great Lakes Plain, and the steeper, more rugged western half, called the Superior Upland, part of the Canadian Shield. The rock in the western portion is the result of volcanic eruptions and is estimated to be at least 3.5 billion years old (much older than the eastern portion) and contains the region's ore resources. Banded-iron formations were deposited 2 billion years ago; this is the Marquette Range Supergroup. A considerable amount of bedrock is visible. Mount Arvon, the highest point in Michigan, is found in the region, as well as the Porcupine and Huron mountains.