Construction on the tunnel began in May of 1844. Using only hand tools and built almost entirely by Irish immigrants, the tunnel was completed in December of that year. Among the many legends surrounding the tunnel is the story that during its construction, a British contractor informed his largely Irish Catholic workforce that they would have to work on Sunday and skip going to mass. One worker became so enraged that he pulled out a pistol and fatally shot the contractor. According to legend, the workers walled the man's body up inside the tunnel, where it presumably still remains.
The tunnel was operational for only sixteen years. Political shenanigans led to its closure in 1859 or 1860 when Brooklyn banned steam locomotives within city limits. The tunnel was ordered filled in and closed off. Unbeknownst to city officials, however, the man hired to fill the tunnel only capped the ends, leaving defunct railroad tunnel largely intact, if mostly forgotten.
As is often the case with disused and mostly forgotten places, the tunnel spawned many legends over the years. There were the obligatory stories of massive, tunnel-dwelling rats; during Prohibition, stories flourished of bootlegging and mushroom-growing in the tunnel, and during World War II, it was rumored to be a hideout for Nazi spies.
In 1980, an engineering student named Bob Diamond, who knew a bit about the tunnel, climbed down a manhole and broke through a brick wall, revealing the long-forgotten tunnel. The tunnel became Diamond's life's work; he led tours into the tunnel for many years and founded the Brooklyn Historic Railway Association in 1982 to promote and preserve the tunnel. At one time, there was talk between Diamond and city officials of opening a museum in the tunnel. Along the way, Diamond and other preservationists got the tunnel added to the National Register of Historic Places.
In 2010, however, the Department of Transportation halted the tours and the city once again ordered the tunnel closed. Diamond sued the city for breach of contract and lost, and as of this writing, the tunnel remains closed to the public.