The Sheppard Subway line was proposed in the report titled Network 2011. Published in 1985, this report laid out a plan for future rapid transit development. Under this plan, three routes were suggested for expansion: the Sheppard Subway line, a Downtown Relief line, and an Eglinton West Rapid Transit line. The Sheppard Subway line was planned to run from Yonge Street to Victoria Park Avenue, and later to be extended west to Dufferin Street and east to the Scarborough Town Centre.
Construction on the Sheppard Subway line began in 1994. The line would consist of five stations: Yonge-Sheppard Station, Bayview Station, Bessarion Station, Leslie Station, and Don Mills Station. Both tunnelling and cut and cover tunnel construction were used to create the line. Constructing the connection between the new line and the Yonge line at Sheppard Station required careful engineering to keep the Yonge line open.
While the Sheppard Subway line was highlighted as a priority for rapid transit expansion, progress did not immediately materialize. In 1990, Network 2011 was reimagined as the Let’s Move Program. This program consisted of more rapid transit lines. The Sheppard Subway line was still part of the plan, but it was no longer considered a priority. In 1993, the Let’s Move Program was rebranded and altered, becoming the Rapid Transit Expansion Plan (RTEP). Under the RTEP, the Sheppard Subway was prioritized once more and cut down in size; now, it would only run between Yonge Street and Don Mills Road.
The Sheppard Subway line opened on November 24, 2002.