Thanks to Toby Weiss and Matt Mourning, I was alerted to a fascinating street in North St. Louis, where the early Twentieth Century architecture switches to Modernist architecture of the mid-century.
Perfectly preserved, and still maintained, these houses face other houses across the street built fifty years before.
Expect a more detailed and more informative post from B.E.L.T. in the near future.
Update: Toby Weiss has posted a much more detailed post on this fascinating block here.
There appears that nothing was ever on this spot, despite being in the heart of the city. Nearby Handy Park was apparently a quarry, and perhaps they used this block for storage.