His name was Nathaniel Gordon, and he was a mariner hailing from Maine. Born in 1824, he was caught in 1860 attempting to bring a batch of West African captives across the Atlantic to sell into slavery. This was a crime that had been nominally punishable by death since 1820; however, previous slave traders had only been slapped with a fine or miniscule prison time, or had gotten off scott-free. Nat Gordon got the dubious honor of becoming a scapegoat.
Gordon was sentenced to death by hanging, and the sentence was carried out in February of 1862, during a low point in the Union's fortunes during the Civil War. He went to his death drugged and semi-coherent; he had nearly managed to cheat the hangman the night before thanks to a bottle of poison he had been carrying on his person during his imprisonment.
Many expressed opposition to the execution, particularly because Gordon had a young son, and his beautiful wife showed passionate devotion to her husband during his trial. Both his mother and his wife interceded to Mary Todd-Lincoln on his behalf, and many letters were written to President Lincoln pleading for clemency. Lincoln's only response was to chillingly recommend that Gordon get his heart right with his Maker.
Gordon's execution is one of the more obscure events in American history, but the following is a superb account: