The last surviving witness to the assassination of President Abraham Lincoln actually appeared on a tv game show in 1956. Mr. Samuel Seymour appeared on "I've Got a Secret" in this video:
A newspaper published an interview with the Mr. Seymour:
In February 1956, two months before his death, 96-year-old Samuel J. Seymour appeared on the CBS television show "I've Got A Secret." His secret: he witnessed Abraham Lincoln's assassination when he was five years old.
Sure enough, Seymour has been widely recognized as the last surviving person in America who had been present at Ford's Theatre the night of Lincoln's assassination on April 14, 1865.
According to the Washington Times, Seymour attended the Ford's Theatre performance as a young boy with family friends. He was told upon arriving in Washington, “Sammy, you and I and Sarah are going to a play - a real play. And President Abraham Lincoln will be there."
Seymour's recollection of the event includes a shot ringing out, someone in the President's box screaming and Lincoln slumping forward in his seat. He also caught a glimpse of John Wilkes Booth jumping from the box to the stage.
Link to newspaper interview.