Summer 1998

Limestone soil saved natural area from development, allows rare dolomite prairie species to grow

Will County, Illinois

Lockport Prairie is a lost wonder worth discovering. Nestled against the Des Plaines River to the east and the Chicago & Illinois Western Railroad to the west, this 254-acre strip offers a rare glimpse of an almost pristine dolomite prairie.

Here a shallow limestone soil restricts the prairie plants' roots that normally grow six to eight feet deep. It is in this unique environment that rare dolomite prairie species can grow. Some areas drain quickly and dry out in summer, providing conditions for more rare plants of parched ground. Elsewhere, the water table wells up through the dolomite bedrock, forming marshes and fens.

The varied habitats — dry and mesic prairies, marshes, sedge meadows, and fens — provide environments in which more than 100 species of rare native plants and animals thrive.

The Des Plaines River Valley, in which Lockport Prairie is located, was the outlet for Glacial Lake Chicago during the Pleistocene Age. When the glaciers retreated some 12,000 years ago, large volumes of water flowed through the valley, eroding it to bare bedrock. As a result, the shallow soil contains elements leaching up from the limestone.

It is just this shallow soil that may have been Lockport Prairie's saving grace. Because of its unsuitability for farming, this land was purchased for the construction of the Chicago Sanitary and Ship Canal.

Then it sat for decades, an unknown remnant of pre-settlement Illinois. When a visitor stands in the center of the trail and scans eastward across the tops of a myriad of purple meadow rue, old witch grass, big blue stem, and wild raspberries and plum, "natural history" becomes visually literal. Lockport Prairie allows a rare glimpse of this region's living past.

Discoveries don't end at the trail. One may see state-endangered spotted turtles, the federally-threatened lakeside daisy, or the federally-endangered Hine's emerald dragonfly, which was first discovered here in 1983. That year, too, the site was dedicated as a state nature preserve. The federally-endangered leafy prairie clover, one of North America's rarest plants and found in only three locations in the state of Illinois, dwells here as well. Prior to the discovery of the clover here, the last record of the plant in Illinois was more than 70 years ago.

On a sunny afternoon, one might see flocks of egrets wading and kingfishers darting at the marshes' surface for a tasty snack. A favorite spot for many visitors, however, is the natural spring in the center of the trail to the left that offers up diamonds of icy water drops in the prairie heat.

Stop, sit down on the roughly-hewn flat bridge that spans the spring, and drink in a gem: the Lockport Prairie Nature Preserve. Lockport Prairie is owned by the Metropolitan Water Reclamation District and managed by the Forest Preserve District of Will County. For information, call (815) 726-3306. As a dedicated state nature preserve, there is plenty of nature but no picnic area or rest rooms.

— Sharon L. Comstock