The Johnstown Flood: The Incredible Story Behind One of the Most Devastating Disasters America Has Ever Known is a definitive account of the catastrophic failure of the South Fork Fishing and Hunting Club dam on June 30, 1889. In less than an hour, over two million tons of water swept through the Pennsylvania valley, killing more than 2,000 people and destroying entire neighborhoods in Johnstown. David McCullough reconstructs the disaster with a focus as much on the negligence that allowed it to happen as on the tragedy itself — a landmark work of American nonfiction.