The center two drivers overhang the rails a lot more than the outer two. I'd guess this is part of the way these huge machines handle corners.

Anyone know what the big slabs are stacked up on the left side of the picture?

Her sister locomotive (6755) is at the Railroad Museum of Pennsylvania.

Looks like the signal bridge down there is still there, at 39.97706N 75.1928W, with the river just beyond it.

This looks like a Grif Teller painting waiting to be colorized. Grif was a legendary PRR calendar painter for 30 years. Beautiful artwork.

The Pennsy was, of course, known for its extensive electrification; the NYC to DC stretch was, by some accounts, the longest in the world, and would have been nearing completion in 1935. What's less discussed is to what extent steam operation continued on those same tracks; passenger and freight e-loks were developed, so I don't think it would have been strictly necessary, and certainly the exhaust would have been damaging to the catenary, but I'm guessing it still continued, to some extent, regardless.

I've often wondered how much the smoke & steam from those locomotives interfered with the performance of the overhead catenary wires. Surely they had to be cleaned every so often.