Complex sentence: The advent of the railway dramatically increased the numbers of immigrants arriving, commerce and industry, as had the Lake Ontario steamers and schooners entering port before, which enabled Toronto to become a major gateway linking the world to the interior of the North American continent.
Split into simpler sentences: The advent of the railway dramatically increased the numbers of immigrants arriving, commerce and industry, as had the Lake Ontario steamers and schooners entering port before. These enabled Toronto to become a major gateway linking the world to the interior of the North American continent.