Johnstown, Penn. Destroyed by Flood

On May 31, 1889, the earthen dam holding back 20 tons of water in a man-made lake ruptured, and the water flowed downstream, decimating the mill town of Johnstown, killing 2,209 people. Trees were uprooted, entire buildings destroyed, and hillsides were stripped down to bedrock. A look at what happened, why, and how.