The valley of the Conemaugh in which Johnstown stood lies between the steep walls of lofty hills. The gathering of the rain into torrents in that region is quick and precipitate. The river on one side roared out its warning, but the people would not take heed of the danger impending over them on the other side—the great South Fork dam, two and a half miles up the valley and looming one hundred feet in height from base to top. Behind it were piled the waters, a great, ponderous mass, like the treasured wrath of fate.
The South Fork Reservoir was the largest in the United States, and it contained millions of tons of water. When its fetters were loosened, crumbling before it like sand, a building or even a rock that stood in its path presented as much resistance as a card house. The dread execution was little more than the work of an instant.