Although most railways of central and eastern Canada were initially built to a 5 ft 6 in broad gauge, there were several, especially in Atlantic Canada and Ontario, which were built as individual narrow-gauge lines. These were generally less expensive to build, but were more vulnerable to frost heaving because vertical displacement of one rail caused greater angular deflection of the narrower two-rail running surface. Most of the longer examples were regauged starting in the 1880s as the railway network began to be bought up by larger companies.

The Toronto and Nipissing Railway (T&N) was the first public narrow-gauge railway in North America. It chartered in 1868 to build from Toronto to Lake Nipissing in Ontario, Canada, via York, Ontario, and Victoria counties. At Nipissing it would meet the transcontinental lines of the Canadian Pacific, providing a valuable link to Toronto. It opened in 1871, with service between Scarborough and Uxbridge. By December 1872 it was extended to Coboconk, but financial difficulties led to plans of the line being built further abandoned at this point. The railway merged with the Midland Railway of Canada in 1882.