I always point out that slavery wasn't that long ago, but it's really hard to illustrate the point. Louis CK's joke that the period between now and slavery is two old ladies back to back helps. It also helps to know that John Tyler, born in 1790 and president in 1840, still has grandsons alive today.
Via Rebecca Rosen, here's another illustration -- video of an eyewitness to the murder of Abraham Lincoln. It's interesting that the hosts claims that Lincoln's death was only "indirectly" related to the Civil War. Reunion was, then, still in effect.