This natural obstacle on the main route into the continent played a decisive role in the establishment and the development of Montréal as a major centre of trade, production and distribution. Here the river rushes through a narrow channel strewn with boulders and small islets. For travellers going inland, the rapids were a major impediment to transportation on the St. Lawrence. Both travellers and goods had to pass overland from Montréal to Lachine; descending the river, they could risk shooting the rapids. It was not until the opening of the Lachine Canal in 1825 that a navigable route to the interior was developed.