From Ohio History Central
The Black Swamp was located in the northwestern part of Ohio. Native Americans refused to live in the foreboding region. It consisted of dense forests, and for much of the year, the land was flooded. By 1820, most of Ohio was settled and no longer was part of the frontier. The only exception to this was the Black Swamp area. Later in the nineteenth century, Ohioans drained the swamp. This area now consists of some of the most fertile agricultural land in the entire United States.