"Marijuana" is a Chicano slang name for "hemp" and wasn't brought into use in the United States until the 1900s. So, Abraham didn't know about "Marijuana" itself, per se. There is a letter, often disputed, supposedly written by Lincoln--possibly in hopes of receiving a free harmonica or cleaning kit in the mail, in exchange for his endorsement--to the Hohner Harmonica Company, some time just after their founding in 1857 and just before the President's 1865 assassination. The letter is alleged to state: "Two of my favorite things are sitting on my front porch smoking a pipe of sweet hemp, and playing my Hohner harmonica." -Abraham Lincoln The letter is supposed to be hung in the Hohner museum, but curators have long insisted its not being there. It is possible that no letter ever existed and just as possible that a Lincoln fanatic stole it while on a museum tour. Lincoln, himself, was never popularly known to be a smoker.

Certainly not as a recreational drug. Marijuana was used for medical purposes in the 1800s, but IF Lincoln used it, he would not have smoked it. It would have been a minor ingredient in a 'tonic' or 'elixir.'