II.

Physical Geography

Wisconsin ranks 22nd in size among the states. It covers 169,639 sq km (65,498 sq mi), including 4,740 sq km (1,830 sq mi sq mi) of inland water. Also under jurisdiction of the state is 24,237 sq km (9,358 sq mi) of waters in lakes Michigan and Superior. Wisconsin is roughly rectangular in shape, except for the Door Peninsula, which is about 130 km (about 80 mi) long and separates Green Bay from Lake Michigan. Wisconsin has a maximum length from north to south of about 480 km (about 300 mi) and a width from east to west of about 450 km (about 280 mi).

A.

Natural Regions

Wisconsin is customarily divided into two major natural regions, or physiographic provinces, each of which is a part of one of the broader physiographic divisions of North America. The two natural regions are the Central Lowland and the Superior Upland. The Central Lowland, which is a part of the larger physiographic division known as the Interior Plains, covers southern Wisconsin. The Superior Upland, a southward extension of the Canadian Shield, or Laurentian Upland, occupies northern Wisconsin.

The Central Lowland is the larger of the two natural regions. It is a predominantly low-lying area and swings in a broad belt across the southern two-thirds of the state. Over the eastern part of the region the underlying rocks have been covered by thick deposits of glacial clays and sands known as till, or drift. Most of this glaciated area is referred to as the Eastern Lake section of the Central Lowland, but a small area in the south is a continuation of the Till Plains, a section that covers adjoining areas of Illinois. During the Ice Age, which ended about 10,000 years ago, a number of ice sheets pushed southward across Wisconsin and adjoining areas. These ice sheets planed off the hills of the preglacial landscape, filled up the ancient valleys, and created the fairly smooth plain that now covers most of the southeast.

The unglaciated Wisconsin Driftless section of the southwest is believed to look the way the rest of the Central Lowland looked before the Ice Age. Some sections, especially those south of the Wisconsin River, are quite rocky, steep, and rugged, but most land is only moderately hilly and is suitable for farming. Among the more prominent features are the Military Ridge, Blue Mounds, and Baraboo Range, which provide sweeping views of the countryside. Unusual for this part of the country are the steep-sided, flat-topped hills found in the vicinity of Camp Douglas that are similar in appearance to the mesas and buttes of the arid Western states.

The Superior Upland occupies northern Wisconsin and is underlain by ancient and very hard rocks. The region is higher than the Central Lowland and for this reason is sometimes referred to as the Northern Highland. Most of its hills are from 400 to 430 m (1,300 to 1,400 ft) above sea level. Several isolated peaks rise considerably above this level, however. They include Timms Hill, which at 595 m (1,951 ft) is the highest point in Wisconsin, and Sugarbush Hill, Rib Mountain, and the Gogebic, or Penokee, Range. Forests cover much of the Superior Upland, and there are numerous small lakes of glacial origin. A low-lying and partially swampy plain, known as the Lake Superior Lowland, occupies the areas along the southern shore of Lake Superior.

B.

Rivers and Lakes

The rivers of Wisconsin drain into either the Mississippi River system, which flows southward into the Gulf of Mexico, or into the Great Lakes-St. Lawrence system, which flows eastward into the Atlantic Ocean.

The Mississippi is the only river in Wisconsin navigable by commercial vessels, and for its entire length in the state it forms part of the Minnesota border and all of the Iowa state line. Its principal tributaries in the state are the Saint Croix, which also forms part of the Minnesota state line, and the Chippewa, Black, Rock, and Wisconsin rivers. The principal rivers draining into Lake Michigan are the Menominee, which forms part of the Michigan state line, and the Fox and its tributary the Wolf River. Several small streams drain into Lake Superior.

Wisconsin has many lakes. In addition to lakes Superior and Michigan, there are nearly 9,000 smaller lakes scattered over the surface of the Superior Upland and Central Lowland. The largest natural lake is Lake Winnebago, which covers 534 sq km (206 sq mi). Other lakes include Lake Pepin, which was formed behind silt that acted as a dam on the Mississippi River; Green Lake; and lakes Poygan, Mendota, and Koshkonong. The largest artificially created lakes are Petenwell and Castle Rock reservoirs on the Wisconsin River, Lake Chippewa, and Flambeau Reservoir.

C.

Climate

Wisconsin has a humid continental climate. Winters are long and cold throughout the state. Summers are short and fairly hot, especially in southern Wisconsin. The waters of lakes Superior and Michigan modify the climate of the coastal areas to a noticeable extent. These areas are generally milder in winter and cooler in summer than interior sections of the state.

C.1.

Temperature

Average July temperatures range from more than 22° C (72° F) in the southwest to less than 19° C (66° F) in some northern areas. Daytime temperatures are seldom much higher than 32° C (90° F), and cool weather is not unusual. Summer nights are generally cool, and July temperatures have been known to dip to the freezing point in northern areas. January averages fall below freezing throughout Wisconsin. They range from less than -12° C (less than 10° F) in the interior northern areas to -6° C (22° F) in the southeast, along the Lake Michigan shore. During winter extremely cold weather persists for several weeks at a time.

C.2.

Precipitation

Average annual precipitation ranges from 700 to 800 mm (28 to 32 in). Rainfall is generally heaviest during the spring and summer, and snowfall is generally moderate in the south, but can be quite heavy in the north. Thunderstorms, sometimes accompanied by devastating tornadoes, are common in spring and summer, particularly in the southern part of the state.

C.3.

Growing Season

The growing season ranges from less than 90 days in some areas of the north to more than 160 days along parts of the Lake Michigan shore. Land situated within about 3 km (about 2 mi) of Lake Superior has an extended frost-free period averaging 114 days.

D.

Soils

Spodosols, which are generally acidic, coniferous forest soils of sandy outwash and loamy till, cover most of the northern one-third of the state. These soils are seldom used for agriculture in Wisconsin. The gray-brown alphasols that are found to the south are more productive, although applications of lime and fertilizer are needed to maintain their fertility. It is on these soils that Wisconsin’s prosperous agriculture has developed. Areas of fertile prairie soil exist in the southern quarter of Wisconsin, and there are scattered areas of bog and alluvial soil in the state.

E.

Plant Life

Extensive forests once covered most of the state. They now cover 46 percent of the state’s land area. Most forest land in Wisconsin is privately owned.

Northern Wisconsin is covered by forests of northern hardwoods mixed with conifers. Around the beginning of the 20th century, young pioneer species of hardwoods replaced the stands of white pines destroyed by deforestation in the 19th century. The aspen and birch are the two most common trees in these second-growth forests, with sugar maple (the state tree) also appearing. Other trees in the northern forests are the white pine, red pine, jack pine, basswood, spruce, hemlock, and red maple. Shrubs of the area include the blueberry, raspberry, beaked hazel, chokecherry, bog rosemary, and red-berried elder.

The hardwood forests of southern Wisconsin are dominated by red and white oaks, hickories, maples, and basswoods. Beeches occur in the extreme east of the state. Characteristic shrubs in the southern forests are the chokecherry, dogwood, Juneberry, poison ivy, staghorn sumac, and prickly ash.

F.

Animal Life

Wisconsin’s animal populations have endured many changes in the past century. The black bear is once again growing in number, while the resident population of timber wolves remains on the state’s endangered list. The Canada lynx, an infrequent visitor to Wisconsin, is also on the list of endangered species. Elk have been reintroduced to the northwestern portion of the state, as have the fisher and pine marten in the northern forested areas. Among the mammals found throughout Wisconsin are the white-tailed deer, muskrat, woodchuck, red fox, coyote, skunk, raccoon, mink, otter, beaver, cottontail, flying squirrel, and gray squirrel. Mammals found in some parts of Wisconsin include the badger, opossum, gray fox, porcupine, and snowshoe hare.

Wisconsin lies on the Mississippi Flyway, one of the migratory paths followed by millions of birds each spring and fall. Among the waterfowl commonly seen in Wisconsin during the migrations are Canada geese and several species of wild ducks. Horicon Marsh, in south central Wisconsin, is a major stopover for migrating waterfowl.

Upland game birds include the ring-necked pheasant, Hungarian partridge, sharp-tailed grouse, bobwhite, ruffed grouse, and woodcock. Hawks and owls are common, and wild turkeys have made a remarkable comeback in recent years. The Wisconsin River is known for its sizable population of bald eagles. Songbirds include the robin, the state bird, and juncos, house finches, English sparrows, nuthatches, cardinals, blue jays, bluebirds, tufted titmice, red-winged blackbirds, western meadowlarks, and prothonotary warblers. Also found in the state are flickers; hairy, downy, and red-headed woodpeckers; yellow-bellied sapsuckers; crows; and ravens. The cedar waxwing summers in the state.

Among the popular game fish are the muskellunge, northern pike, walleye, lake trout, largemouth and smallmouth bass, perch, bullhead, and crappie. The lake sturgeon and shovelnose sturgeon were once abundant but have become quite rare in Wisconsin waters, along with the true paddlefish, which is now protected.

G.

Conservation

Reforestation, soil erosion, and wildlife management are the principal concerns of conservationists in Wisconsin. The Wisconsin Department of Natural Resources is the agency responsible for carrying out state conservation programs. Federal agencies concerned with conservation in Wisconsin include the United States Forest Service, the United States Natural Resources Conservation Service, and the United States Fish and Wildlife Service.

In 2006 Wisconsin had 37 hazardous waste sites placed on a national priority list for cleanup due to their severity or proximity to people. Progress was being made in efforts to reduce pollution; in the period 1995–2000 the amount of toxic chemicals discharged into the environment was reduced by 20 percent.