The Great Black Swamp covered approximately 1,500 square miles in northwest Ohio and northeastern Indiana and formed when the Wisconsin Glacier retreated about 20,000 years ago, leaving a flattened surface covered with impermeable clay. Sand ridges separated certain areas of the swamp and provided some higher ground. As a result of the Treaty of Greenville in 1795, Native Americans from all regions of Ohio were forced into this area, established villages along the edges of the swamp, and used the swamp as a very fertile hunting ground. Beginning in the 1840s, it took several generations of determined farmers to drain Ohio's "Last Frontier" and turn it into the rich farmland of today. Plant material from the area's dense forests fell and decomposed, turning the water black and giving the Great Black Swamp its name.
