Although the idea of quilts being used as secret guides to help slaves escape from the south has great romantic appeal, Underground Railroad research has found no evidence that such a practice occurred. For more information New Jersey's Underground Railroad Myth-Buster covers several UGRR myths including the one about quilts. He has also written a critique of the book, "Hidden in Plain View. Another good resource is "The Underground Railroad Quilt "Code": Betsy Ross redux" for an excellent rebuttal to some of the recent promotion of this myth as truth. For an indepth background on the Underground railroad go to Putting it in Perspective: The Symbolism of Underground Railroad Quilts.
On the other hand many quilts have been made commemorating the Underground Railroad. To view some of these stunning quilts go to Threads of Freedom: The Underground Railroad Story in Quilts.
There is so much more to African American quilting history than the idea that quilts might have been used in the UGRR. Consider finding other sources of information about Black American quilting than the Underground Railroad quilt myth. I encourage you to visit African American Quilts: A Long Rich Heritage to learn more.