[pj3000]

I don't see why it's surprising that Detroit would sprawl more to the north and west than it does to the south... just given the orientation of where the core city is and how it was laid out. Add in that established cities like Pontiac and Flint were major players in the auto industry right along with Detroit and you have even more reason for growth in that direction. Development grids are naturally going to extend out to the NW.

And with heavy industry naturally locating along the Rouge River and Detroit River to the south, I would guess that the suburbs in that direction are mainly 1950s to 70s era, without much newer sprawl. That's pretty common.