Whenever you see rows of identical double houses like these in a suburban area or out in the country, you have run across an old mining town. The houses were usually built all at once to provide housing for the workers, who would live on the property of the mining company and be paid in scrip accepted at the company store, and thus have strong incentive to remain loyal employees rather than homeless paupers. These little houses were built very cheap, but often under the supervision of a skillful architect who knew how to make cheap permanent.
Mollenauer, now part of the municipality of Bethel Park, was built in 1902 by the Pittsburgh Terminal Coal Company for workers in its Mine No. 3. After the mine passed into private ownership, the houses were sold off individually. Originally the houses on a street all looked the same—though the steep hill forced some adaptations, as we see on 1st Street above, where houses on one side have basements with ground-level street entrances, and houses on the other side have their front porches down several steps from the street.
With separate owners, the houses in a pair often end up going their separate ways as if they hardly knew each other. The one on the left side of this pair looks as though it has fallen into the hands of house-flippers.
A 1934 plat map shows us how the village was laid out.
Mollenauer is a short stroll from the Washington Junction station.