Lewis and Clark Corps of Discovery

When Captains Meriwether Lewis and William Clark led their Corps of Discovery through this region in the summer of 1804, the Hills were covered with prairie. The scant trees that existed hugged the water ways. At that time, Oto and Missouri tribes lived in the southern part of the Hills and the Omaha in the mid-section of the Hills.

Change Comes to the Loess Hills

Around the 1850's, change came to the Loess Hills.  Farms, communities and roads checked the wilderness that had cleansed the prairie of the always encroaching trees and woodland plants and, as you can see now, trees blanket most of the hills.  Of the prairie that had covered the Hills, only 22,000 acres remain with about 4,500 acres being in the Broken Kettle Grasslands, the largest self-sustaining parcel of prairie in Iowa.

Now surrounded by forests and developed lands, the pockets of prairie in the Hills are islands of prairie flora and fauna not found until hundreds of miles to the west and not seen elsewhere in Iowa.  Among these animals are the prairie rattlesnake (only in a very small area near Westfield in the northern Hills), plains pocket mouse, upland sandpiper, zebra swallowtail, ornate box turtle and plains spadefoot toad.  Among the plants are ten-petal blazing star, spear grass, tumble grass and prairie moonwort.  The native yucca is in the easternmost limit in North America.

Unique Features of the Loess Hills

The Loess Hills have some features that are unique because of their soil.

First, if you look at a hill through which a road has been cut or part has been removed (usually for fill elsewhere), you will see its cross-section is almost uniformly loess.  Only in the northern and southern reaches of the Hills are rocks naturally exposed.

Second, if you were to remove the topsoil from the slope of a Loess Hill, the exposed Loess will erode like sugar when saturated.  Local people call the loess soil "sugar clay" for this reason.  Even when covered with topsoil, loess can slump, most often in a unified manner across a slope creating the characteristic "cat step" ledges seen on some grassy hills.

Oddly though, cut a Loess Hill vertically and its wall can stand for decades due to the interlocking characteristics of the loess soil particles.