sentences:  Travellers began to use the trails by the 1820s, with the heaviest use from the 1840s to the early 1870s, when they were superseded by railways.Until then, these cartways provided the most efficient means of transportation between the isolated Red River Colony and the outside world.They gave the Selkirk colonists and their neighbours, the people, an outlet for their furs and a source of supplies other than the Hudson's Bay Company, which was unable to enforce its monopoly in the face of the competition that used the trails.