Grain elevators have been on this site since 1876, first in wood, then wood and iron, and after the precarious use of lard-oil torches, finally concrete in 1913. The 'S' on the side refers to D.G. Stewart, who founded the D.G. Stewart Elevator and Feed Mill in 1873. As of 1928, It used to have a 4-storey red brick warehouse adjoining it, but this burnt down in March 2012 and was only recently cleared away, as the bulldozers show. Its future is likely to be tied into hotel development. The building is built against a hill, and on the second storey (third in USA) the building opens out to a rail track, running beneath the trees in the picture below. It was from here the unprocessed grain arrived.
The main elevator, the first concrete one to be built in Pittsburgh and after its predecessor burnt down, fireproof. Ironically the warehouse adjoining it burnt down months before we arrived. Inside the structure was still mostly solid looking though.

We arrived in Pittsburgh late, and were tipped off about the place by GE080, and quickly climbed the stairs to the top room. A ladder fixed to the wall lead up to a platform, but there wasn't a connection to the roof. I climbed back down and found a knackered looking wooden ladder. With Fishbrain's help, we got the ladder into place, and Fishbrain braved the climb up to the roof portal. The sun had set by this point, and a calmness hung in the air.

A gorgeous view of the Pittsburgh skyline, and the point where the Monongahela and Allegheny River merge to form the Ohio River, which flows left on the picture below.

Moving down to a lower roof, there was various pieces of graffiti, including a Shepherd Fairey 'Andre' piece on the far left, unlikely to be an original.

I returned the following morning to get some decent shots, while Fishbrain opted to do some live skyscraper infiltration. I brought my facemask along, as the air was heavy with grain dust. In the top floor of the building, on a floor smaller than the larger floors below, a set of semi-automatic scales for weighing the grain in large tranches. I also found an old bottle of Mountain Dew here.

Stairs up to the top floor, a loading chute runs up to a hopper.

The discharge spout from the grain bin on the 'fourth level.'

This is a grain cleaner, a self-explanatory piece of machinery.

Drag conveyors with spouts in the background feeding hoppers scales and passing grain from the scales to storage bins.

Stairs leading down from the second floor from the top referred to officially as the '4th level'.

On the third level of the building can be found this corn dryer.

On the right behind me on the ground floor is a cross conveyor, for moving grain between warehouse and elevator.

Fishbrain & I chill out on our first night in Pittsburgh, taken on the lower roof.

Every exploration has its merit point, and with an abandoned site, it's always a pleasure to take one's time walking around without fear of being busted. Conversely, the merit of doing an infiltration 'is' the fear of being busted!
More pictures of the buildings in use can be found here.
History and details are taken from the HAER site (History of American Engineering Record).

The silo was sadly demolished not long after our trip here, an empty gravel area now remains.