First External Cardiac Pacemaker, 1950
In 1950, in Room 64 of the Banting Institute at the University of Toronto, Drs. Wilfred Bigelow and John Callaghan successfully paced the heart of a dog using an external electronic pacemaker-defibrillator having implanted electrodes. The device was developed by Dr. John Hopps at the National Research Council of Canada. This pioneering work led to the use of cardiac pacemakers in humans and helped establish the importance of electronic devices in medicine.
Plaque via Alan L. Brown's site Toronto Plaques. Full page here.