Interesting. So maybe it's a Baby Boomer phenomenon? Wish the data went back further, doesn't look like the Census started monitoring this before 1948. With some Googling it looks like federal home-ownership assistance efforts (either through providing subsidized housing or tax relief) started as far back as the Great Depression. Maybe people just wanted houses and prior to such programs it was unattainable for most?

Looks like a good topic for a book for anyone who has the time. I'm sure it's a confluence of several factors. :)