It turns out that I hadn’t quite run out of things to say about the second Madison Square Garden. Above, a circa 1910 view from the park, where you can just make our Diana and her bow on top of the tower. Below, the 1899 Sanborn map:
The purpose of the Sanborn maps was to judge the safety of buildings against fire hazard, so that insurance companies could set their rates. The detail that is provided on the maps all comes back to that central point. So, for example, the reason that MSG is referred to as, plural, “buildings” is that it was composed of a number of district structures that would have different problems with fire risk and fire-fighting. The small-footprint portions facing Madison Avenue, to the west – the Garden Theater, the Concert Hall, the Assembly Rooms, and the Tower – were of fairly ordinary fireproof construction for the era, but well compartmentalized. The stage area for the theater is called out separately because that was a known risk. The big open space of the main arena was quite different. The solid lines indicate interior masonry walls that could serve as fire compartmentalization.
“Buildings of Superior Construction except Roof over Arena (boarding)” is a fascinating note. The building exceeded the usual standards for fire-protected construction, except for the largest portion of the roof, which was composed of wood boards. Oops. I suspect that was a weight savings for the long-span trusses that supported that roof, given that the only practical fireproof alternate in 1890 would have been tile arches, at a weight something like ten times as high as plank. Here’s a view of the arena roof from the east, taken shortly before demolition in the 1920s:
That catwalk is a track that was definitely used for training and may have been used for some events. Here it is, below, with Harvey Cohn (a track athlete and coach) on the left and Joseph Hagan (AKA Philadelphia Jack O’Brien), a boxer, on the right, working out in the rain. My guess is that Cohn was working as an endurance trainer for Hagan.
You can see the arena roof up close here, and it’s tar and gavel over the wood plank.