1 year after people:Abandoned ships on the Great Lakes drift towards the Niagara Falls but are stopped on the Niagara River by the International Railway Bridge. The bridge does have an enemy however. In the time of humans, every year before winter a large boom would be strung across the end of Lake Erie to prevent ice from entering the Niagara River. But now that there are no humans to deploy the boom ice begins to assualt the bridge.
20 years after people:The International Railway Bridge collapses due to ice damage and the way to Niagara Falls is open.