When Abraham Lincoln delivered the Gettysburg Address, he was weak and dizzy; his face had a ghastly colour. That evening on the train to Washington, DC, he was febrile and weak, and suffered severe headaches. The symptoms continued; back pains developed. On the fourth day of the illness, a widespread scarlet rash appeared that soon became vesicular. By the tenth day, the lesions itched and peeled. The illness lasted three weeks. The final diagnosis, a touch of varioloid, was an old name for smallpox that was later used in the 20th century to denote mild smallpox in a partially immune individual. It was unclear whether Lincoln had been immunized against smallpox. Indeed, this review suggests that Lincoln had unmodified smallpox and that Lincoln's physicians tried to reassure the public that Lincoln was not seriously ill. Indeed, the successful conclusion of the Civil War and reunification of the country were dependent upon Lincoln's presidency.