Stillfork Swamp occurs in a broad valley in the Western Allegheny Plateau Ecoregion. The wetlands were formed by a complex series of events related to Pleistocene glaciation. Blockage of the pre-glacial Dover River caused the Stillfork Valley to fill with water, forming a finger lake. Deposits from the surrounding hills gradually filled the valley, forming a slack-water silt terrace. The resulting broad, flat, and poorly-drained land created favorable conditions for the various wetland communities to develop.
The entire swamp encompasses over 600 acres within the Stillfork Valley and its major tributaries and is drained by Stillfork Creek, a small, slow moving stream characterized by an extremely low gradient. Stillfork Creek now flows into Sandy Creek, and into the Tuscarawas River. Beaver utilize the area to a great extent.
Examples of other species that can be found at this preserve include:
- Plants: water-starwort—an Ohio state listed plant
- Birds: American bittern, least bittern, marsh wren, green heron, swamp sparrow, common snipe, Virginia rail
- Amphibians/Reptiles: spotted turtles