It looks like that was only just before construction started.
You can see the old aerial photos of the city here:
https://maps.calgary.ca/CalgaryImagery/Imagery/
It looks like the block was full of low-rise buildings, probably similar to a lot of the older buildings that still survive along 7th and 8th Ave today, into the early-80s. Even up to 1984, it looks like most of the buildings on that block were still standing.