A few months after the foundation excavation started, in the winter of 1927, the first steel was erected at 15 Broad Street. The cranes, the riveted built-up columns, and the column splices are all details I’ve pointed out in other old construction photos. This one happens to clearly show the temporary guy wires used to true the steel. There are quite a few wires visible within the portion of the frame that had been erected.
If you think about it, the process of making sure the columns are plumb is more difficult at the beginning of the project, when there’s no steel already erected and trued to use as a comparison. Having this first area (six bays wide, three bays deep) trued made it easier to deal with the rest.