Big history nerd here and I figure some of you might share my interest in studying how places change over time. I recently found this web site containing hundreds of historic NTS topo maps of Ontario. https://ocul.on.ca/topomaps/collection/
The years seem to range from early 1900s through to the 1970s. Not a complete set by any means, but the quality of the scans is superb. Let me know if you find them useful.