Pymatuning Lake State Park is located on the wetlands surrounding the Shenango River in Ashtabula County, Ohio and Crawford County, Pennsylvania. In 1933, the Pymatuning Lake Reservoir was completed on the river for flood control, water supply, recreation, and fish and wildlife management. In addition to the dam, the Espyville-Andover Highway was completed to cross the lake. However, detailed geologic information of the park is lacking for the public to understand its ancient history. A detailed investigation was conducted to better constrain the geologic history of Pymatuning Lake State Park.

Detailed information of the park was gathered through extensive fieldwork and published data. Bedrock and glacial geologic maps were constructed this data. Thickness of glacial material and bedrock formations were determined using ground water well data. A cross section through the park was produced, showing the geology in the third dimension.

Pymatuning Lake State Park is situated on the glaciated plateau of northeastern Ohio and northwestern Pennsylvania border where Pleistocene glaciers advanced over the gentle hills and stream valleys of the land formerly uplifted as part of the Appalachian Mountain building process. The subsurface bedrock units in the park consist of Devonian shales. The bedrock was covered by several ice advances of the Wisconsinan Glacier that left behind glacial features consisting of the Hiram, Lavery, and Kent ground moraines, and the Defiance end moraine north of the park. These glacial units completely cover the bedrock, leaving minimum exposures in the area.