It is not the Underground Railroad and its existance but the use of quilts to guide that is under discussion. I visited the Uderground Railroad museum in Atlanta a few years ago and the curator was describing the quilt and the signifiance of the blocks.
One block that was of some interest to me was her explanation of the Sun Bonnet Sue block......that block didn't come into existance until the 1930's. Even respected African Amerian quilt historians have disputed the story of the use of quilts in this way.