"Glaciers and glacial action have contributed in a very large degree to the making of our magnificent State. What Iowa would have been had it never suffered from the effects of the ponderous ice sheets that successively overflowed its surface, is illustrated, but not perfectly, in the driftless area. Here we have an area that was not invaded by glaciers. Allamakee, parts of Jackson, Dubuque, Clayton, Fayette, and Winneshiek counties belong to the driftless area. During the last two decades deep wells have been bored through the loose surface deposit, and down into the underlying rocks. The record of these wells shows that the rock surface is very uneven. Before the glacial drift which now mantles nearly the whole of Iowa was deposited, the surface had been carved into an intricate system of hills and valleys. There were narrow gorges hundreds of feet in depth, and there were rugged, rocky cliffs, and isolated buttes corresponding in height with the depth of the valleys.

"To a person passing from the drift-covered to the driftless part of the state, the topography presents a series of surprises. The principal drainage streams flow in valleys that measure, from the summits of the divides, six hundred or more in depth. The Oneota, or Upper Iowa River, in Allamakee county, for example, flows between picturesque cliffs that rise almost vertically from three to four hundred feet, while from the summit of the cliffs the land rises gradually to the crest of the divide, three, four or five miles back from the stream. Tributary streams cut the lateral slopes and canyon walls at intervals. These again have tributaries of the second order. In such a region a quarter section of level land would be a curiosity. This is a fair sample of what Iowa would have been had it not been planed down by the leveling effects of the glaciers. Soils of uniform excellence would have been impossible in a non-glacial Iowa. The soils of Iowa have a value equal to all of the silver and gold mines of the world combined.

"And for this rich heritage of soils we are indebted to great rivers of ice that overflowed Iowa from the north and northwest. The glaciers in their long journey ground up the rocks over which they moved and mingled the fresh rock flour from granites of British America and northern Minnesota with pulverized limestones and shales of more southern regions, and used these rich materials in covering up the bald rocks and leveling the irregular surface of preglacial Iowa. The materials are in places hundreds of feet in depth. They are not oxidized or leached, but retain the carbonates and other soluble constituents that contribute so largely to the growth of plants. The physical condition of the materials is ideal, rendering the soil porous, facilitating the distribution of moisture, and offering unmatched opportunities for the employment of improved machinery in all of the processes connected with cultivation. Even the driftless area received great benefit from the action of glaciers, for although the area was not invaded by ice, it was yet to a large extent covered by a peculiar deposit called loess, which is generally connected with one of the later sheets of drift. The loess is a porous clay, rich in carbonate of lime. Throughout the driftless area it has covered up many spots that would otherwise have been bare rocks. It covered the stiff intractable clays that would otherwise have been the only soils of the region. It in itself constitutes a soil of great fertility. Every part of Iowa is debtor in some way to the great ice sheets of the glacial period.

"Soils are everywhere the product of rock disintegration, and so the quality of the soils in a given locality must necessarily be determined in large measure by the kind of rock from which they were derived.

"From this point of view, therefore, the history of Iowa's superb soils begins with first steps in rock making. The very oldest rocks of the Mississippi Valley have contributed something to making our soils what they are, and every later formation laid down over the surface of Iowa, or regions north of it, has furnished its quota of materials to the same end. The history of Iowa's soils, therefore, embraces the whole sweep of geologic times.

"The chief agents concerned in modifying the surface throughout most of Iowa since the disappearance of the latest glaciers have been organic, although the physical and chemical influences of air and water have not been without marked effect. The growth and decay of a long series of generations of plants have contributed certain organic constituents to the soil. Earth worms bring up fine material from considerable depths and place it in position to be spread out upon the surface. They drag leaves and any manageable portion of plants into their burrows, and much of the material so taken down into the ground decays and enriches the ground to a depth of several inches. The pocket gopher has done much to furnish a surface layer of loose, mellow, easily cultivated and highly productive soil. Like the earth worm, the gopher for century after century has been bringing up to the surface fine material, to the amount of several tons annually to the acre, avoiding necessarily the pebbles, cobbles and coarser constituents. The burrows collapse, the undermined boulders and large fragments sink downwards, rains and winds spread out the gopher hills and worm castings, and the next year, and the next, the process is repeated; and so it has been for all the years making up the centuries since the close of the glacial epoch. Organic agents in the form of plants and burrowing animals have worked unremittingly through many centuries, and accomplished a work of incalculable value in pulverizing, mellowing and enriching the superficial stratum, and bringing it to the ideal condition in which it was found by the explorers and pioneers from whose advent dates the historical period of our matchless Iowa."