They finally realized that it was the lack of noise. They had all become so used to the roar of the water rushing over the falls that the silence they were hearing was deafening!
Many of the townsfolk dressed for the chill and gathered at the river to watch.
The flow of water was stopped completely over both falls on March 29th, 1848 due to an ice jam in the upper river for several hours. This is the only known time to have occurred. The Falls did not actually freeze over, but the flow was stopped to the point where people actually walked out and recovered artifacts from the riverbed!
Enjoy these vintage photos from a freeze in 1911! The reports are that it also froze in 1932. A small trickle of water always found it's way past the jam, so it was never frozen solid.