Meetings of Parliament
After the burning of the Parliament Buildings on the night of 3rd February, 1916, the House of Commons assembled in this building on the 4th and the Senate on the 8th February. Parliament met here for the last time on 10th November, 1919, and assembled for the first time in the rebuilt Parliament Buildings on 26th February, 1920.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.