It was the first new Toronto streetcar route in many years, and the first to employ a dedicated tunnel, approximately 600 metres (2,000 ft) long.

The "Harbourfront" route name disappeared until 2000, when the Queens Quay streetcar tracks were extended west to Bathurst and Fleet Streets.

[4][5] In July 2012, Waterfront Toronto began a major reconstruction of Queens Quay West, requiring the 509 streetcar to be replaced with buses for the duration of the construction.

[6] On 12 October 2014, streetcar service resumed on 509 Harbourfront route after an absence of over two years in order to rebuild the street to a new design, and to replace tracks.

TTC service planner Scott Haskill suggested that "public realm and urban design" drove the Queens Quay redevelopment at the expense of transit planning.

[8] Transit advocate Steve Munro analyzed the route's performance for May 2016 and concluded that the extra running time was consumed from Queens Quay Loop to the intersection of Bathurst and Fleet streets, and that the running time east of Spadina Avenue was the same as before the reconstruction because of fixes to traffic signal problems.

Pending the conversion of the overhead on other streetcar lines, runs to and from the carhouse continue to use trolley poles, with the changeover taking place at Exhibition Loop.