This building was formerly used to repair and store passenger locomotives for the Canadian Pacific Railway, and was constructed prior to the opening of Union Station. Upon completion, it was one of the most advanced roundhouses of its day and remains an important example of facilities and technologies available during Toronto's railway age. For 20 years after its construction this was one of the busiest and most important roundhouse complexes in Canada. The Roundhouse complex was closed by CP in 1982, used by Via Rail until 1986, and was designated as a National Historic Site in 1990. The first 11 bays were disassembled and rebuilt between 1994-1997 to allow for alternate uses in the building.

This National Historic Site currently houses the Steam Whistle Brewery, The Rec Room, and the Toronto Railway Museum. The railway turntable, dating from 1929, has recently been restored.

Renovations to this building won an Honourable Mention from the Toronto Architecture and Urban Design Awards in the "Building Adaptation" category in 2000.

A Historic Sites and Monuments Board of Canada plaque at the site reads:

This roundhouse complex was built by the Canadian Pacific Railway in 1929 to service the steam locomotives of its passenger trains using nearby Union Station. The 32-stall roundhouse featured the most modern technology. Its direct steaming facility was the first of its kind in Canada, allowing a faster and more economical operation, and a smokeless environment. Abundant natural light is provided by its monitor roof and large windows. The switch from steam power to diesel, completed by the CPR by 1960, spelled the end for Canadian roundhouses. The John Street complex was closed in 1982.

• Architect - IBI Group  <-- More buildings by this architect.
• Architect - Hotson Bakker Architects  <-- More buildings by this architect.
• Architect - J.M.R. Fairbairn  <-- More buildings by this architect.
• Developer - CP Rail
• General contractor - Anglin-Norcross Limited
• Owner - Metropolitan Toronto Convention Centre