And even some of the top tier engineering schools that have admitted women for an even longer time generally had a pretty minuscule number until relatively recently.

no, it really wasn't that long ago.

I'd like to think that 55 years ago isn't really that far in the past but, at the scale of undergraduate academic institutions it sort of is. Although I think it was always coed going back to the 1800s, I think MIT still had just a handful of women in a class into the 1960s.