Strong men could then easily haul a loaded canoe over these wooden rollers until it could be launched again in the water.

Often these portages were made to circumvent dangerous rapids or waterfalls.

The Indians and the French Canadians soon learnt how to steer canoes down rushes of water--rapids--which we should think very dangerous on an English river; but of course many of the rivers were obstructed at intervals by descents of water which no canoe could traverse up or down, and in these cases a path was cut from one smooth part of the river to another, and the canoe carried or hauled overland.
In this way the great French and British explorers found it possible to travel by water from the Atlantic to the Pacific Ocean across a width of land of something like 2500 miles.

The only serious walking that had to be done was the crossing somewhere or other of the Rocky Mountains, where the streams, of course, were far too precipitate in descent to be navigable.

In the hot, dusty plains of Assiniboia and the upper Missouri region the Amerindians had introduced horses, obtained indirectly from Spanish Mexico, and these were of great service to the white pioneers, especially in their pursuit of the bison.
So much for the summer season, when the rivers were full and overflowing, and the ground consisted of bare rock, sand, or soil covered with vegetation; the abundance of navigable streams and the suitability of the country to horses rendered very little walking necessary for those who wished to traverse the Canadian Dominion from end to end.
But the winter changed these conditions, the rivers became coated with thick ice, and the ground was covered, except in steep places, with an unvarying mantle of snow.