The current bridge over the Genesee River near Portageville (originally Portage), New York is less than four years old, despite being on a rail line constructed around 1851 by the Erie Railroad. The river, which runs more or less north to Lake Ontario, is in a deep gorge at this crossing, so a high bridge is necessary. The 2017 steel trussed-arch bridge replaced an 1875 wrought iron trestle, with short Pratt-truss spans supported on a series of rectangular towers. The 1875 bridge replaced the original bridge, seen above, a timber trestle that opened in 1852. That’s the bridge I want to talk about.
I came across this by accident, when I found the 1870 picture below with the arty caption “Horse Shoe Falls, 70 feet high, Genesee River, N.Y.”:
The falls are very nice, but what is that behind them? It turns out it’s the Erie’s wood trestle. Here’s another arty picture:
And here’s a better view of the trestle structure:
Unlike Herman Haupt’s wood trestles constructed during the Civil War, this was meant to be a permanent bridge. Or rather, “permanent,” since US railroad structures of the mid-1800s were constructed with the knowledge that they might soon be obsolete and replaced.
It’s impossible to discuss the context of this bridge without discussing the state of the Erie Railroad. It was one of the early east-west main lines in the US and it was spectacularly mismanaged throughout its history, sometimes by accident and sometimes deliberate and for the profit of parties other than the road itself. Its main line, from New York to Buffalo and then on to Chicago, managed to miss most of the larger cities in upstate New York. For example, Rochester, the city closest to the Genesee gorge, was at the end of a branch of the Erie, while it was a way station on the main line of the New York Central. The Erie was the first major railroad in the US to ever go bankrupt, and it spent a great deal of its history flirting with bankruptcy.
There’s nothing structurally impossible about carrying trains – particularly the relatively small trains of the 1850s and 60s – over a wood trestle. As the pictures show, it was a dense web of heavy timber and there are no records of it being structurally inadequate. However, steam engines produced a lot of sparks and cinders; inevitably, the wood trestle was destroyed by fire. Its replacement was iron because that had become the standard material for railroad bridges in the years after the first bridge was built.
A note on the structural form of the bridge. The huge mass of timber that occupies most of the photo is a series of closely-spaced towers set on masonry foundations in the river and the surrounding gorge. The bridge itself is the series of smallish double-diagonal trusses that run from tower to tower. The most striking design elements overall are the top and bottom knee braces everywhere in the towers that verticals meet horizontals. They are not trusswork, but rather a reasonable way to cut down the unbraced length of the tower’s compression verticals and the unsupported span of the trusses at the top.
In short: it was pretty but doomed by the coming increases in train weight. Had it not burned, it would have been replaced anyway.
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