Fort Defiance occupies the southern tip of Cairo, Illinois, at the meeting of the Ohio and Mississippi rivers, a location whose strategic importance reaches from the Mississippian era to the Civil War, when it was known as Camp Defiance. Archaeological evidence indicates warfare here long before American settlement, and French trader Pierre Laclède was among the first known Europeans to land on what is now the southern end of Illinois. The site’s geography made it militarily valuable as a gateway into the interior. Today it is also notable as the lowest point in Illinois and part of the state’s southernmost park, now managed under Illinois state stewardship.