The city of Middlesboro is located within an impact crater east of I75 near the Kentucky-Tennessee border. This can be no question that an impact formed the Middlesboro basin - both shatter cones and high pressure quartz have been found there. These are created during impacts. The impact affected Pennsylvanian layers, so must have happened less than 310 million years ago.
The following is from a pair of aerial photographs obtained from the Kentucky Geological Survey. The city is in the lower left, and the rim of the impact feature is visible in the right portion.
The following is a cross section showing the rock layers below Middlesboro.
