During the last ice age almost all of Canada, along with parts of Europe and Asia, were buried beneath one to two miles of ice. At the same time, sea levels stood 350 to 400 feet lower than today.
Sea levels were so low that the entire continental shelf, at least in eastern North America, was above water. Many states on the eastern seaboard were twice as big as today. New Jersey’s shoreline, for example, stood 60 to 100 miles east of its present location.
Same in the west.
The land between Alaska and Asia rose out of the sea like a bridge (or rather, the sea dropped away from the land), and the Bering Strait, which today is only 18 stories deep at its deepest point, was above water. Our ancestors could have walked to Siberia. (The word bridge is misleading, because the land connection between Alaska and Siberia was almost as wide as Alaska itself.)