The Great Black Swamp

The Great 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...
It stretched roughly from Fort Wayne, Indiana in the west, eastward to the Ottawa National Wildlife Refuge near Port Clinton along the Lake Erie shore, and from (roughly) US 6 south to near Lima and Findlay. Near its southern edge at the southwestern corner of present-day Auglaize County, the swamp was so impervious to travel that wheeled transportation was impossible during most of the year, and local residents thought the rigors of travel to be unsuitable for anyone except adult men...
Although much of the area to the east, south, and north was settled in the early 19th century, the dense habitat and difficulty of travel through the swamp delayed its development by several decades. A corduroy road (from modern-day Fremont to Perrysburg) was constructed through the Maumee Road Lands in 1825 and paved with gravel in 1838, but travel in the wet season could still take days or even weeks. The impassibility of the swamp was an obstacle during the so-called Toledo War (1835–36); unable to get through the swamp, the Michigan and Ohio militias never came to battle. Settlement of the region was also inhibited by endemic malaria. The disease was a chronic problem for residents of the region until the area was drained and former mosquito-breeding grounds were dried up.