Lincoln's last scene in the movie is implied to be the day of his assassination, which is grim in and of itself and all, but Fridge Horror sets in when you look up the details of Will Johnson's real life. As it turns out, he died of small pox, and Lincoln arranged and paid for the burial; put two and two together and you realize Will must have already been long dead during that final scene (i.e. the last day of Lincoln's life.) For all the ass-kicking he did alongside Abe during the film, he just ends up unceremoniously dying of a disease off-screen.
The movie mentions when the silver weapons aren't on the train that there is more than one railroad into Gettysburg. Which railroad? The Underground Railroad!