Fort Defiance, known as Camp Defiance during the American Civil War, is a former military fortification located at the confluence of the Ohio and Mississippi rivers in the city limits of Cairo, in Alexander County, Illinois. The strategic significance of the site has been known since prehistoric times with archaeological evidence of warfare dating to the Mississippian era. It is the southernmost park in the state of Illinois. At 279 feet (85 m) in elevation, Fort Defiance Point is also Illinois' lowest point.[1]