From 1870 — five years after the end of the Civil War — to 1883, the Brooklyn Bridge was built with no power tools, no heavy machinery, and only a basic, evolving understanding of how to make steel:
Both of the towers of the Brooklyn Bridge are in the water of the East River. Ever wonder how you dig a big hole in the bottom of a river bed? In the late 1800s? It’s called a caisson, which is a huge, watertight wooden box half the size of a city block. This monstrosity was constructed on the river, sealed with pine tar, and carefully floated to a specific location on the river. It was then slowly sunk to the riverbed by placing stone on top that would eventually become the foundation.Done, right?
Wrong. With the caisson on the riverbed, it’s time to push it another 45 feet into the riverbed in search of bedrock. Workers did this through the continued application of stone to the top while workers in the caisson dug out the riverbed with shovels, buckets, and, when necessary, dynamite. There was nothing resembling an electrical grid, so there was nothing resembling modern lighting in this watertight pine-tarred box, which was slowly descending through the floor of the East River. There were no jack hammers, so when they hit rock, they used small amounts of dynamite to crack these rocks. In a pine-tarred box, at the bottom of a river, mostly in a very wet dark.
And when the caisson finally hit bedrock 45 [feet] underground, they had to do it all over again for the New York tower. 30 feet deeper.
The chief engineer ended up bed-ridden from caisson disease — which divers now call the bends:
As the New York caisson descended further than its Brooklyn counterpart, the incidents of the bends increased, killing two men. With no bedrock in sight, Roebling used his knowledge of geology and mineralogy to make an amazing decision: stop digging. It wasn’t bedrock, but it was compacted sand.The New York tower. 78 feet deep into the riverbed. Resting on sand. It hasn’t moved.