The Great Black Swamp (also known simply as the Black Swamp), was a glacially fed wetland in northwest Ohio and extreme northeast Indiana, United States, that existed from the end of the Wisconsin glaciation until the late 19th century. Comprising extensive swamps and marshes, with some higher, drier ground interspersed, it occupied what was formerly the southwestern part of proglacial Lake Maumee, a holocene precursor to Lake Erie. The area was about 25 miles (40 km) wide (north to south) and 100 miles (160 km) long, covering an estimated 1,500 square miles (4,000 km2). Gradually drained and settled in the second half of the 19th century, it is now highly productive farm land. During the second half of the 20th century, efforts were undertaken to preserve and restore portions of the swamp