At the end of the Pleistocene Epoch, when most of the northern North American continent was covered with glaciers, vast amounts of moisture were "tied up" in the ice. This had the effect of lowering the level of the oceans, so that large areas which would otherwise have been submerged under the sea were dry land.
In the Bering Sea, the emergence of a broad land bridge between Alaska and Siberia during the periods of glaciation allowed people to move gradually eastward from Asia into the New World. From Beringia (the Bering Land Bridge), their route south followed an ice-free corridor between the Cordilleran Mountain glaciers and the continental Laurentide ice sheet to the east. As indicated on the map, a major portion of the present-day United States (including parts of Alaska) and a section of the Yukon Territory were not covered during the last of the Pleistocene glaciations. With the gradual retreat of the massive ice sheets about 15,000 years ago during the end of the Pleistocene, plant and animal life, including man, moved into the newly exposed areas along the margins of the ice.
It appears that between 11,000 and 15,000 years ago, people moved southward through an ice-free corridor between the mountain ice areas of the Rockies to the west, and the massive Laurentide ice sheet to the east emanating from northern Hudson Bay. The precise route followed, after they reached the regions south of the ice, can only be sketched from archaeological traces of early encampments found in southern Canada and the United States. The occurrence of "early man" sites across the United States and southern Canada suggests that people spread very rapidly and adapted easily to new natural surroundings.
Glacial ice in the Maritimes began to recede about 15,000 years ago. In their continual search for food and other resources, people reached the Maritimes some 10,000 to 11,000 years ago.
