Like many buildings on the southeast side of Liberty Avenue, where the two grids of our eighteenth-century street plan collide, the Baum Building is forced into a triangle. It began its life as the Liberty Theater, but it lasted for only a few years before being turned into offices. Now, under the ownership of the Pittsburgh Cultural Trust, it has gone back into the entertainment business as an art gallery.
Addendum: The architect was Edward B. Lee. The theater was built in 1912; the conversion to offices was done in 1920, and Father Pitt suspects Lee supervised that as well. See this page in The Brickbuilder from 1913 for a picture of the building as originally built.