Minnesota's surface features were formed primarily by glaciers during the last Ice Age. Only a small area in the southeast, in the so-called Driftless Area, was left untouched.
During the glaciation, massive sheets of ice eroded and smoothed the hills and in places leveled the land. On receding, the glaciers dammed rivers, created lakes, and left widespread debris.
Minnesota lies in two major physical regions of the United States: the Central Lowlands and the Superior Uplands.
The Central Lowlands region consists mainly of level to rolling plains. All of the state except the northeast is in this region. In the northwest is the broad, fertile valley of the Red River of the North, known simply as The Valley in Minnesota. It is exceptionally flat and was once part of the lake bed of Lake Agassiz. There are also large stretches of flat plains north and south of the Minnesota River and in the far north beyond Red Lake. Swamps, marshes, and peat bogs are widespread in some northern parts of the state.
The Superior Uplands region, in the northeast, is part of the vast Canadian Shield. It is largely a flat to rolling upland where ancient, hard, crystalline rock is either exposed at the surface or slightly covered by glacial debris. In places the terrain is broken by fairly prominent hills and low ranges, including the iron-rich Mesabi Range.
Scenic cliffs extend along some sections of Lake Superior's shore. Eagle Mountain, in the Misquah Hills in the extreme northeast, is the highest point in the state—2,301 feet (701 m) above sea level. The lowest elevation—600 feet (183 m)—is the surface of Lake Superior.Minnesota's state tree is the Norway pine.
Minnesota's rivers and lakes are among the state's chief scenic and recreational attractions. This is reflected in two of the state's nicknames—Land of 10,000 Lakes and Land of Sky-blue Waters.
A small part of Minnesota is drained by rivers flowing into Lake Superior. In most of the state, drainage is either southward to the Gulf of Mexico by way of the Mississippi River system or northward to Hudson Bay via the Nelson River system. The Mississippi drains the largest part of the state. Major tributaries include the Minnesota River, which joins the Mississippi near the Twin Cities of Minneapolis and St. Paul, and the St. Croix River, which forms part of the Minnesota-Wisconsin border.
The chief rivers draining northward toward Hudson Bay are the Red River of the North, along the North Dakota border, and the Rainy River, along the Ontario border.
Waterfalls and Whitewater rapids mark the courses of many rivers, especially in the hillier areas of the northeast. Some wilderness areas, particularly the Boundary Waters Canoe Area, are accessible only by water.
Minnesota has more than 15,000 lakes of 10 acres (4 hectares) or more in size. Red Lake, divided into upper and lower sections, covers 451 square miles (1,168 km 2)and is the largest lake entirely within the state. Other large lakes within Minnesota include Mille Lacs, Leech, Winnibigoshish, and Vermilion. Lake of the Woods and Rainy Lake are on the Canadian border.
Minnesota has a humid continental type of climate. It is determined mainly by the state's location in the center of the continent, which aids rapid seasonal heating and cooling of the land. Winters are long and severely cold; summers are short and warm to hot.
Average January temperatures increase from roughly 2° F. (-17° C.) in the northwest to 18° F. (-8° C.) in the southeast. During July, average temperatures vary from about 65° F. (18° C.) to 76° F. (24° C), increasing from north to south. Only in the vicinity of the Misquah Hills does the July average fall as low as 59° F. (15° C). Extreme temperatures occasionally rise to more than 100° F. (38° C.) and sometimes drop below -40° F. (-40° C). Normally, the growing season is between 90 and 170 days, depending on location.
Annual precipitation varies from as little as 19 inches (480 mm) in the extreme northwest to 32 inches (810 mm) in the southeast. Most of it comes in the form of rain during the growing season. The annual snowfall is roughly 20 to 70 inches (510 to 1,780 mm), increasing from southwest to northeast. Tornadoes and blizzards are among the storms that occasionally strike the state.
Very little of Minnesota's natural vegetation remains. Coniferous forests, mainly pine, spruce, and fir, once occurred throughout most of northeastern and north-central Minnesota. These forests were cleared long ago by loggers and in most areas have been replaced by poplar, aspen, birch, second-growth conifers, and various kinds of scrub.
Deciduous forests—predominantly oak, hickory, maple, beech, and birch—at one time extended in a broad band from around Brainerd southeastward to the Iowa border. They were the first forests cleared in Minnesota, making way for farming. The rest of the state—the south and the west—was originally a vast expanse of tall prairie grass. Most of the area now is highly productive farmland.Minnesota's state flower is the pink and white lady's-slipper.