Topography. Northern Minnesota is an extension of the Laurentian highlands—ancient rocks smoothed down to moderate relief. The surface here is rolling, is densely covered with pine forests, except in the western part, and abounds in lakes and swamps. Southern Minnesota is largely prairie, wide expanses of gently rolling, grassy, and generally treeless plains of boulder-clay, belted with moraines. The greater part of the surface is young, the plains are as yet undissected, and lakes still remain in the moraines. In the southeastern and southwestern corners of the State the old surface was not covered over by the later Wisconsin glacial sheet, and here we find the surface has weathered smooth and the lakes have disappeared. The surface of the State has as its central feature, in the north-central part, an elevated plateau, which rises 1750 feet above the level of the sea. From this plateau the country slopes off north, south, east, and west, reaching, however, 2200 feet in the northeast in the Mesabi Mountains north of Lake Superior, and after a considerable decline rising again in the southwest corner of the State to 1800 feet in the Coteau des Prairies. The average elevation is 1200 feet, or 600 feet above the level of Lake Superior. The surface is unbroken by any sudden uplifts, and the slope from the central plateau in each direction is very gradual. The lowest portions of the State are the region around the head of Lake Superior, and the southeast section of the State where the land falls to an elevation of about 600 feet.
The rivers of Minnesota radiate in all directions from the central plateau mentioned above. The two principal drainage systems are those of the Mississippi and the Red River of the North. The Mississippi rises in the Itascan lake group, and with its two large tributaries, the Saint Croix on the eastern boundary, and the Minnesota in the west, drains more than one-half the State. The Red River of the North, which drains the western slope, flows northward on the western boundary through a flat lacustrine basin to Lake Winnipeg. The northern and northeastern slopes are small in area and drained by short streams flowing into the Rainy River and Lake system on the northern boundary, and into Lake Superior. The largest of these streams is the Saint Louis River, which flows into the western extremity of Lake Superior. The Mississippi River alone is used for navigation; the Minnesota and the Red River are reported ‘navigable,’ but are little used. The direction of the rivers, as well as the position and formation of the innumerable lakes dotting the surface of the State, have been determined by glacial action. In the north the lakes are usually cut out of the old rock and display bold tortuous shores. In the south the lakes are often broad and shallow. Three-fourths of the lakes of the State are those occupying the undrained hollows in the morainal deposits, which cover the greater portion of the surface of the State; others, such as Lakes Pepin, Traverse, and Big Stone, are river expansions. The lakes vary in size from mere ponds up to Red Lake, with an area of 340 square miles. The other more important lakes are Leech and Winnibigashish in the plateau region; Mille Lac; and Minnetonka, a popular summer resort for Minneapolis and Saint Paul.
The most important lacustrine feature of Minnesota is the extinct Lake Agassiz. An incident in the recession of the Pleistocene ice was the ponding of the marginal drainage of the ice sheet in the valley of the Red River as fast as it was uncovered by the melting ice. A great lake was formed which has been called Lake Agassiz. At its largest stage it has a maximum width of nearly 700 miles, and drained through the Minnesota River into the Gulf of Mexico. On the disappearance of the ice, and the draining out of Lake Agassiz by the Nelson River, its bed was left as a level alluvial plain.
Climate and Soil. Minnesota lies in the middle of the north temperate zone, and in the geographical centre of the continent. This gives it a continental climate, with marked extremes of temperature. The average temperatures for January are 15° F. at the southeastern corner, and at the northwestern corner only 1° or 2° F. For July it is 70° F. in the south and 65° F. in the north. Maximum shade temperatures rise above 100° F. over all the State west of Duluth, while the minima are 40° F. below zero in the southern and northeastern counties and 50° F. below in the extreme northwestern, thus giving a range of 150° degrees or over for Red River Valley. The annual rainfall ranges from 20 inches in the northwest to over 30 inches in the southeast. The rainfall is characterized by a scant precipitation in the winter season, and moderately heavy rains during the crop season. There is an average annual snowfall of 20 inches in the southwestern part of the State, which increases gradually to 80 inches at Pigeon Point. The southern counties have an average annual relative humidity of less than 70 per cent., rising steadily northward to 75 per cent. in the northwestern counties. The average velocity of the wind is 8 miles per hour in the east, and almost 11 miles per hour at Crookston, which is the highest inland average velocity recorded in America. The average path of the northwest cyclones passes through the southern counties. Between 300 and 350 such storms occur in ten years. The prevailing wind is west in the northern half and southwest in the southern half. The climate on the whole is rigorous in winter, though mild and even occasionally hot in the southern counties in summer. But the nights are always cool, and the air dry, making the whole State a favorite summer resort.
The soils of the State are wholly glacial, and since the outcropping stratified rock is largely limestone, most of the soil derived from this source is extremely rich—a black and finely comminuted loam. On the older drift in the southeastern counties, for 30 to 40 miles back from the Mississippi River, there is a coating of loess, an extremely fine black loam of great fertility. Where the Cambrian sandstone outcrops in the east central part of the State, considerable areas are covered with a light sandy soil, not at all encouraging for agriculture. In the old land of the northeast and north central counties there are large areas almost denuded of soil, or covered with a scanty coating of granitic drift. In the Valley of the Red River the silts of the extinct Lake Agassiz occur, a fine black soil of almost incomparable richness, constituting some of the best wheat lands in the world.
Geology. The northwestern corner of the State formed a part of the old Archæan continent, and its east central portion was in Archæan times occupied by a large island. These areas now
