In 1954, the TTC opened Canada's first underground rail line, then known as the "Yonge subway", under Yonge Street between Union Station and Eglinton Avenue with 12 stations. As of 2018, the network encompasses 75 stations and of route. In , the system had a ridership of , or about per weekday as of , making it the busiest rapid transit system in Canada in terms of ridership.
