The last time Niagara Falls froze: March 1848.
Water flow was interrupted by accumulation of small icebergs in the upper section of the river; both falls froze quickly then.
In the lower section, an "ice bridge" linked both banks for miles; locals and tourists invaded this ice cap , taking photos, toboganning, selling drinks.
In fact, the tremendous flow of water remained under the ice cap, so this could break at any time and cause disaster.
