Click an image below to view an online brochure. Click an image below to view a video. One of the most outstanding features of Harrison County is the Loess Hills and the Loess Hills State Forest.
The State Forest in Harrison County is divided into three management units - Little Sioux, Mondamin and Pisgah. The Little Sioux unit lies between the communities of Little Sioux and Pisgah and is comprised of 3,752 acres. The Pisgah unit’s 2,567 acres are located east of Pisgah. This unit is also the site of the forest headquarters and Brent S. Olson Memorial Visitor Center, which is located at 206 Polk St. (two blocks west of Hwy. 183) in Pisgah. The Mondamin unit is located east of the town of Mondamin and contains 1,097 acres. A fourth management unit of the forest, Preparation Canyon, is located in Monona County and is just a few miles north of Pisgah. It contains 4,402 acres of forest.
The forest areas in the three Harrison County units are open to hunting, except within 200 yards of residences. All forest
units are open to hiking, cross country skiing, bird watching, scenic driving and nature study. Parking areas for visitors can be found along the various roadways throughout the forest. The Little Sioux unit has several stocked fishing ponds, as well as a picnic shelter off of 138th Trail.
No camping is allowed in any of the units in Harrison County, but camping can be found nearby at Pisgah City Park Campground (712-456-2301), Willow Lake Recreation Area (712-647-2785), Loess Hills Hideaway Cabins (712-996-5003), Preparation Canyon State Park (712-456-2924), Missouri Valley City Park (712-642-3502), and Monona County Conservation Board (712-433-2400).
Preparation Canyon State Park in Monona County is on 342 acres connected to the northeast portion of the state forest. It features hiking trails, picnic shelters and eight backpacking campsites. It is closed to hunting.
History of the Loess Hills
The Loess Hills of western Iowa were formed from 20,000 to 10,000 years ago of finely ground wind blown silt from the glacial deposits. As the Pleistocene glaciers melted, the Missouri Valley became a major channel for tremendous amounts of water. Each winter season, as the quantity of melt water was reduced, large areas of flood-deposited sediments were left exposed to the wind. Silt, clay and fine sand were lifted by the wind, carried to the east and deposited.
The bedrock of Harrison and Monona Counties is limestone upon which lies a mantle of drift, sand, gravel, loess and alluvium. It determines most of the surface features in the counties today.
Three layers of loess have been deposited in the Loess Hills-Loveland, post-Kansan and post-Iowan. The Loveland loess is a water deposit formed during the melting of the Kansan Glacier. It is a compact, heavy, reddish clay which is very sticky when wet, and it is highly valuable in the dry hills because of its ability to retain moisture.
The post-Kansan loess is fine and compact and light blue in color. It takes up moisture slowly when wet but retains it relatively well. Iowa’s Loess Hills The post-Iowan loess is the immediate subsoil of the upland regions of the hills. It can occur up to 90 feet in depth, deeper closer to the Missouri River. It breaks vertically into irregular columns causing frequent slippage and faulting at the surface.
The thickness of the loess and differences between the soils formed in the loess are related to the distance from the source of the loess. The loess is the thickest in the bluffs, reaching more than 200 feet deep in some areas. In places, mainly on steep hillsides adjacent to stream valleys, the Wisconsin loess has been removed by geologic erosion.
The soils of the Loess Hills State Forest were formed in loess, alluvium and glacial till; most soil series formed in a loess parent material. Loess is yellowish-brown, wind-deposited material consisting largely of silt particles. This specific soil forming factor is what gives Iowa’s Western Loess Hills their name as well as their peculiar form. The steep bluffs, comprised solely of loess soil, rise to between 150 and 250 feet above the Missouri River bottom land. The native vegetation of these soils was almost exclusively prairie grasses, with some timber along streams and drainage ways.
The steep, ridged topography, combined with the special physical properties of loess, create some problems in the Loess Hills. The angles of the slopes often range from 50 to 75 degrees. The loess, composed primarily of coarse silt particles, has a very low sheer strength when water-saturated, so that often it cannot bear its own weight.
However, when relatively dry, the loess develops a greater apparent cohesion; this allows the loess to maintain the spectacularly bold bluffs and ridges-forms along the Missouri River valley. These special soil properties impose some serious limitations on any development involving roads and buildings.
Loess is easily eroded by running water. This factor, combined with its collapsibility, contributes to another major problem - soil erosion and resultant gullying, results in detrimental conditions for many aquatic species in the area’s streams and rivers.
Wildlife of the Loess Hills
The Loess Hills of western Iowa exhibit a unique diversity and abundance of wildlife species. The Hills, once home to black bear, elk, buffalo, antelope and wolves now support populations of smaller animals.
The change occurred with the settlement of the land in the 1800s and early 1900s that transformed the prairie cover to agricultural land and woodlands. These new land covers brought new and varied species of wildlife. Species such as the prairie chicken, prairie rattlesnake and plains pocket mouse were replaced by white tailed deer, raccoon, quail, pheasant and wild turkey.
Loess Hills Plant Life
The Loess Hills are predominantly populated with prairie and hardwood trees. The bur oak is the most common tree due to its ability to grow on dry sites and to withstand fire. Others found in the area include red oak, black walnut, hickories, basswood, elms, ashes, Kentucky coffee tree, cottonwood, ironwood and red cedar. The forest contains many natural prairie areas comprised of big and little bluestem, Indiangrass, sideoats grama and forbs such as yucca, pasque flower and lead plant.
A governmental shared-cost cooperative effort with landowners in past years has helped restore Loess Hills lands to its natural prairie landscape in many areas.