Pittsburgh's Chinatown was demolished for the construction of (and subsequent additions to) the Boulevard of the Allies and highway construction in the early 1920s thru 1950s.
It was small, but once stretched to the Monongahela River wharf, interspersed among the warehouses that were once numerous in the area, with 185 Chinese restaurants, shops, and laundries. The red outline shows the general historical extent of where Pittsburgh's Chinatown was, and the green shows all that remains.
These 3 buildings (2 of them restaurants) are pretty much all that remain:
"Chinatown" is now centered in the Squirrel Hill neighborhood, with a boom in Asian restaurants, influx of international Asian student residents, night markets, and where the lunar new year parade takes place. It's an interesting mix with the strong presence of Orthodox and Hasidic Jewish population.