"Mr. Hopper is supposed to have resorted to underground methods as early as 1787."
Print from 'The underground railroad from slavery to freedom' by W. H. Siebert (New York : Macmillan, 1899). Schomburg Photographs and Prints Division (Slavery - Abolitionists).
Electronic reproduction. Marlborough, Wiltshire : Adam Matthew Digital, 2007. Digitized from a copy held by Schomburg Center for Research in Black Culture, The New York Public Library.
Schomburg Center for Research in Black Culture, The New York Public Library