New Urbanists like to make a fuss over the notion of a mixed-use building, touting it as a revival of a long-lost art. While the basic, common-sense notion of people living and working in close proximity certainly did fall out of favor in the 1960s through the 1980s, it never really vanished entirely. And at the height of the 1950s suburban building boom, small-scaled mixed use was actually surprisingly common in Chicago's southern and western neighborhoods.
Main Street, Skokie
"Mixed-use" generally implies some combination of office, retail and residential, and that's generally what you'll find on these commercial buildings. Some feature apartments above storefronts, with generous porch space marked by wood or decorative metal railings.
Western Avenue - more photos here
Others feature upstairs space of a less clear nature. Behind those walls could be office space, either separate or joined with the retail space below, or living space.
The most exciting ones share a similar design vocabulary of materials and style, with an emphasis on angles: angled brick wing walls, angled panels of Roman brick with limestone borders, angled wood roof overhangs.
63rd Street - Midway Lounge
You can find a crop of one-story, single use commercial buildings in the same neighborhoods that use the same design vocabulary, with angled sections of facade and roof overhangs, often trimmed in red wood or red Roman brick.