gs-- Amazing detail. That's the best map I know of for locating businesses in that period. It's interesting that today residential development is reasserting itself downtown--the history of the area in the first couple of decades of the 20th century involved commercial development overtaking residential at an incredible clip. One day there's a block of not-so-old Victorian houses, the next a skyscraper (i.e., the Pacific Electric Building at Main & 6th). Some residential buildings hung on to the '30s--apartment buildings if not detached houses. The Percival, 835 S. Hill:
http://www.csulb.edu/~odinthor/socal8a.html