"Our American Cousin", a once-popular comedy, is the play Abraham Lincoln was watching when he was assassinated at Ford's Theater in Washington, D.C., on the night of April 14, 1865. The play was written by Tom Taylor, an Englishman, and premiered in New York City in 1858—an instant smash. The popular female lead, Laura Keene, would go on to produce and star in the production Lincoln saw seven years later. The play spawned numerous sequels.

Source: Vanity Fair