The story of the quilts comes from one person, now deceased. Her story cannot be substantiated, and in fact, most elements of her story proved to be wrong when research was done on her claims. The woman who has researched teh story the most, Leigh Fellner, tracked down sources near and far (as far away as Ghana and Oxford, England), and has successfully debunked the quilt story. Even without all the docuemtation refuting it, if one pays attention to the details of the myth they are counter-intuitive. Many schoalrs are troubled by its persistance in popular UGRR culture becasue it really tells us nothng about the indivisuslas who took the enormous risks to flee, and those who helped them. NOt oneperson has been linked to the quilt code. UGRR scholars like Art have all been researching this history for decades and not one instance of the code has been unearthed. We researchers know how much of this "secret" history is actually available - it is just buried in archives, libraries, historical scieties, family collections, newspapers, court houses, and other places. The absence of documentation is not proof.
The Follow the Drinking Gourd song is an interesting story. If you read the website Art suggested, you will see that the song we know today was first written and performed by a white folk group in 1947. It is based on a song published in 1928. My take on it is that its roots come from the Alabama region in the post Civil War era when many newly freed African Americans became legally bound to the land they had formerly been enslaved on by unscrupulous farmers who leased land to them in a sharecropping or tenant farmer arrangement. The costs were so high to the newly freed people that they rapidly became indebted to the farmer/landowner and were required by law to stay on the land to work off the debt - a debt they could never work off. This was called debt peonage. Many people so indebted would sneak away in the middle of the night to escape arrest. They would travel north and west to jobs and freedom - just like along the UGRR during the slavery era.
Hope this helps,