The worst flood in United States history occured on June 1st, 1889. The death toll was over 2,200 and was the result of the collapse of the poorly maintained South Fork Dam.
The citizens of Johnstown always worried that the South Fork Dam would collapse, it was abandonded, and then rebuilt by the South Fork Fishing & Hunting Club for recreational purposes. However, eventually this worry became a joke, since it seemed to hold up every downpour. But, after the heaviest downpour ever recored in the South Fork-Johnstown Area, the dam was showing massive failure problems.
The dam's spillway had been blocked by large amounts of debris. Not helped by the fact that the water had risen, 2 inches overnight, and still rising. Throughout the day, workers attempted to fix the dam, but to no avail. At around 3:10 PM, the reconstructed portion that the club did, simply washed off.
Although the major causes of the flood were the initial dam collapse and poor reconstruction efforts, there was also the ignorance of a warning. At around 11:30 AM, the "resident engineer" at the dam, rushed off on horseback to inform the telegraph operator at South Fork to warn the people in the valley below that the dam might collapse. If it had been taken seriously, the death toll may have been much lower, as this was almost 4 1/2 hours before the dam's failure.
When the flood finally hit Johnstown at around 4:14 PM, it survivors said it "sounded like thunder," some knew instantly what it meant however. The whole thing was over in 10 minutes.
If the flood wasn't enough, much of the debris was caught at the old Stone Bridge downstream. Eighty people who survived the flood, died, when much of it caught fire and burned for 3 days.
In the wake of the disaster, every state in the nation contributed some kind of relief, and the people of sixteen foreign countries, including Russia, Turkey, France, Britain, Australia and Germany sent aid. On August 31, 1964, Johnstown was made a national memorial.