Underground Railroad and the Postman

Recently, the NYTimes described how investigators found the person responsible for the story of the Underground Railroad. It smuggled Negro slaves from the US South to the North and even to Canada. This started before the Civil War and ran till the war ended. A beacon of freedom to many. But where did the story originate?

The problem is to dissect thousands of books, newspapers and pamphlets, to traceback the earliest references. But today, thanks to the Internet, archivists have digitised a plethora of documents.