Immense glaciers scoured the earth, removing soil and exposing bedrock. Fine sand, silt, and clay particles from glacial meltwater settled in prehistoric lakes, forming new soil. Changing climate conditions resulted in a warm, dry period, which allowed prairie plants to extend from the Midwest into Pennsylvania.

Gradually the climate became cooler and wetter, more closely resembling our climate today. Eventually, through succession, forests replaced all but a few prairie sites in Pennsylvania.

The Jennings prairie remains due to a thick layer of impermeable clay that prevents most tree species from becoming established. Plants and animals that do live on the prairie must tolerate shallow soils, fluctuating periods of drought and saturation, and fire. Even under these harsh conditions, this ecosystem teems with life.

The 1800s brought an influx of settlers who altered the landscape and depleted the resources through lumbering, agriculture, and hunting. Once the resources above the ground were exhausted, a new generation looked below the surface. Coal mining became a booming industry during this era. While mining provided a needed source of energy, techniques of that day left significant scars on the land.

Dr. Jennings first discovered the prairie in 1905. Thanks to a generous donation from the Butler Garden Club, he initiated the purchase and protection of the area by the Western Pennsylvania Conservancy, a private conservation group. The conservancy was instrumental in establishing environmental education at Jennings.