Photos and Facts: The Johnstown Flood

News clips of recent floods are a grim reminder of one of the great calamities of the late 19th century, the Johnstown Flood. A colossal wall of water sped down a valley and flattened a Pennsylvania town, killing more than 2,000 people.

The photos and facts are still staggering. And so is the knowledge that the disaster could have been avoided.

Photo: Steel Mill Destroyed at Johnstown, 1889

Source: Library of Congress