Also known as Boulevard Saint-Laurent.
Between Rue Prince-Arthur and Avenue Du Mont-Royal*, you'll find these plaques embedded in the sidewalk marking the ages of the adjoining buildings. It is part of Heritage Canada's project designating the busy thoroughfare a National Historic District.
Even if you keep your eyes level, this is always a fascinating street.
*Update: With closer inspection, I see that these plaques extend further north to Mont-Royal.