What we call the Social Enterprise Centre started out as Canadian Pacific Railway Post Office Postal Station A building at 765 Main Street. 

Most people think of travel or transporting goods when they think of the railway, but one of the most important roles it played was mail delivery. 

Built in 1924, Postal Station A was an important part of the nationwide mail system. Mail received from across the country, as well as from folks in Winnipeg, was sorted and sent out through this building. The building also included a section called Immigration hall, which was demolished some time after 1969, leaving the structure as we see it today.

Mail by rail ended in 1971, and 765 Main Street housed several different businesses before BUILD, Manitoba Green Retrofit, and Pollock's Hardware Co-op got together, created a new business called 765 Inc., purchased the building, and transformed into the Social Enterprise Centre in 2012.

The City of Winnipeg has a document on the history of 765 Main, including what it looked like in 2011 just before it was purchased to be renovated into the SEC, which you can read here.