Michigan's two peninsulas are generally level land masses. Flat lowlands predominate in the eastern portion of both peninsulas and in scattered areas elsewhere. The state's lowest point, 572 ft (174 m), is found in southeastern Michigan along Lake Erie. Higher land is found in the western area of the lower peninsula, where elevations rise to as much as 1,600 ft (500 m); the hilly uplands of the upper peninsula attain elevations of 1,800 ft (550 m). The state's highest point, at 1,979 ft (603 m), is Mt. Arvon, in Baraga County.
Michigan's political boundaries extend into four of the five Great Lakes, giving Michigan jurisdiction over 16,231 sq mi (42,038 sq km) of Lake Superior, 13,037 sq mi (33,766 sq km) of Lake Michigan, 8,975 sq mi (23,245 sq km) of Lake Huron, and 216 sq mi (559 sq km) of Lake Erie, for a total of 38,459 sq mi (99,608 sq km). In addition, Michigan has about 35,000 inland lakes and ponds, the largest of which is Houghton Lake, on the lower peninsula, with an area of 31 sq mi (80 sq km).
The state's leading river is the Grand, about 260 mi (420 km) long, flowing through the lower peninsula into Lake Michigan. Other major rivers that flow into Lake Michigan include the St. Joseph, Kalamazoo, Muskegon, Pere Marquette, and Manistee. On the eastern side of the peninsula, the Saginaw River and its tributaries drain an area of some 6,000 sq mi (15,500 sq km), forming the state's largest watershed. Other important rivers that flow into Lake Huron include the Au Sable, Thunder Bay, and Cheboygan. In the southeast, the Huron and Raisin rivers flow into Lake Erie. Most major rivers in the upper peninsula (including the longest, the Menominee) flow southward into Lake Michigan and its various bays. Tahquamenon Falls, in the eastern part of the upper peninsula, is the largest of the state's more than 150 waterfalls.
Most of the many islands belonging to Michigan are located in northern Lake Michigan and in Lake Huron, although the largest, Isle Royale, about 44 mi (71 km) long by 8 mi (13 km) wide, is found in northern Lake Superior. In northern Lake Michigan, Beaver Island is the largest, while Drummond Island, off the eastern tip of the upper peninsula, is the largest island in the northern Lake Huron area.
Michigan's geological development resulted from its location in what was once a basin south of the Laurentian Shield, a landmass covering most of eastern and central Canada and extending southward into the upper peninsula. Successive glaciers that swept down from the north dumped soil from the shield into the basin and eroded the basin's soft sandstone, limestone, and shale. With the retreat of the last glacier from the area about 6000 BC, the two peninsulas, the Great Lakes, and the islands in these lakes began to emerge, assuming their present shapes about 2,500 years ago.