Some that I've seen are:
Dallas
Bug U! This was the old administration building built by the WPA in the '30's and has been recently converted into a nice exhibit for native bugs.
Cat Row Again a WPA exhibit built in 1936 used to hold Lions, Siberian Tigers, Hyenas, Spotted, Black, and Snow Leopards, Pumas, Golden Cats in 12 tiny exhibits. Today it is 5 remodeled exhibits for ocelots, bobcat, and fishing cat. Still an eyesore.
Monkey House Up until 1999 the only monkey exhibit at the zoo and yet again another WPA building. Now is mostly an off exhibit holding facility for birds and a few primates. It was given a new facade and turned into Tamarin Treetops.
San Antonio
Bear Grottoes All the bear grottoes were built in the 1920's and at the time were among the first exhibits anywhere in the country to use a cageless design. Most are surprisingly big for the era.
Fort Worth
Monkey House Small exhibit now in the bird section that obviously holds birds. It belies its current use though with nice mosaics of tamarins and lemurs on its exterior.