With the limited research he was willing to put into it, old Pa Pitt was not able to confirm his impression that this building on Elmer Street was once a stable. But it certainly has the look of a stable. Well into the early twentieth century, the city was full of stables where the thousands of draft horses that pulled every kind of conveyance were kept.
The Allegheny City Stables were built in 1896. If you enlarge the photo (click on it), you can just make out the old sign over the main door:
D.P.W. 8th DIV.
BUREAU OF HIGHWAYS & SEWERS
It’s right across North Avenue from Allegheny West, then the richest neighborhood in Allegheny. Perhaps this was one of the encroachments that induced Allegheny West society to move in a body to Sewickley Heights, where their descendants still live today.
Now, 123 years later, Allegheny West is once again the finest neighborhood on the North Side, and its desirability is spilling across North Avenue. The stable is being renovated and turned into loft apartments, like every other old industrial building.
(And if you notice a familiar picture at the Wikipedia article, it’s because Father Pitt added it himself to show the current state of the building.)