Maine is divided into four main regions: coastal lowlands, piedmont, mountains, and uplands.
The narrow coastal lowlands extend, on average, 10–20 mi (16–32 km) inland from the irregular coastline, but occasionally disappear altogether, as at Mt. Desert Island and on the western shore of Penobscot Bay. Mt. Cadillac on Mt. Desert Island rises abruptly to 1,532 ft (467 m), the highest elevation on the Atlantic coast north of Rio de Janeiro, Brazil. The transitional hilly belt, or piedmont, broadens from about 30 mi (48 km) wide in the southwestern part of the state to about 80 mi (129 km) in the northeast.
Maine's mountain region, the Longfellow range, is at the northeastern end of the Appalachian Mountain system. This zone, extending into Maine from the western border for about 150 mi (250 km) and averaging about 50 mi (80 km) wide, contains nine peaks over 4,000 ft (1,200 m), including Mt. Katahdin, which at 5,267 ft (1,606 m) is the highest point in the state. The summit of Katahdin marks the northern terminus of the 2,000-mi (3,200-km) Appalachian Trail. Maine's uplands form a high, relatively flat plateau extending northward beyond the mountains and sloping downward toward the north and east. The eastern part of this zone is the Aroostook potato-farming region; the western part is heavily forested.
Of Maine's more than 2,200 lakes and ponds, the largest are Moosehead Lake, 117 sq mi (303 sq km), and Sebago Lake, 13 mi (21 km) by 10 mi (16 km). Of the more than 5,000 rivers and streams, the Penobscot, Androscoggin, Kennebec, and Saco rivers drain historically and commercially important valleys. The longest river in Maine is the St. John, but it runs for most of its length in the Canadian province of New Brunswick.