Heavy cables for trolley service extended along the left with a single-circuit, three-phase high voltage route on the right with multipart insulators upon it, once lining this Philadephia-suburban street.

On the left are metal trolley crossarms with heavy-duty pintype insulators upon them. Definite treasure for Lou Hall for sure ;-)

The Philly area as well as Pennyslvania and surrounding states were world-known for their steel plants. So probably metal poles were a bit less expensive than wood ones especially as we see here with heavy trolley circuits and important electric lines.