It’s easy being green… if you’re a bridge.
I was surprised the first time I saw the Golden Gate Bridge; surprised because I was expecting it to be painted gold. Some patient person explained to me that the bridge was so named because it spanned the Golden Gate between the Pacific Ocean and San Francisco Bay.
Before 1931, most steel bridges were black or gray. (The Golden Gate Bridge opened in 1937.) At the time of its design, the St. Johns Bridge across the Willamette River in North Portland was to be painted black, but with yellow stripes — like a bumblebee — to make it more visible to planes taking off and landing at the nearby Swan Island Municipal Airport. David Steinman, the designer said no, his bridge was not going to garishly clash with its verdant surroundings. His design was to complement its environment. The gothic spires were meant to evoke pine trees. Steinman prevailed; the new bridge would be painted “verde green.”
When the St. Johns Bridge opened, it was the longest suspension bridge in the United States. David Steinman went on to design numerous other bridges in Oregon, most famously on the coast, all painted green. What came to be known as ODOT (Oregon Department of Transportation) Green came to be the standard color for thousands of steel bridges around the country. If you need to order some, it’s otherwise known as “federal standard 595 color 24272.”
As time and technology advance, there may be less demand for ODOT Green. More bridges are being made with concrete and new steel bridges are constructed with “weathering” steel which cures to a red rust-like finish that does not need painting. Presumably it’s also impervious to bird guano.