This is a great little museum in Old Montreal. It is inside an old Fire station and is it made up of 3 levels of permanent and temporary exhibitions. The First floor is a permanent exhibition on 5 different stages of Montreal history. This is a very informative exhibition and I found it interesting to compare the history with the locations I know today. The other two levels are made up of temporary exhibition's on Lost Neighbourhoods- the story of three neighbourhoods that disappeared in Montreal and the other a small exhibition on the hidden Mount Royal. I spent a couple of hrs here on my own, I easily could spend more time but there is a lot of reading at the same time you could spend less time especially if you had kids who might get a little bored because it is not that interesting for them I don't think.
Overall, definitely worth a look, especially if you know Montreal and at only $6 entry, not too expensive.