It was opened on December 3, 1844 and was finished by January 1, 1845, as an open cut--that is, a reinforced trench open to the sky. It was built to reduce the grade of the railroad line on its way to the South Ferry at the foot of Atlantic Street (now Avenue), from which passenger could catch ferries to New York City (Manhattan Island).
Five years later a "sturdy brick arch" was placed over the cut, making it a true tunnel. As built, the tunnel was 21 feet wide, 17 feet high and 1,611 feet long.
Insofar as it carried railroad trains under a city street, it could be described as the first subway built in the world, though unlike a modern rapid transit subway, it had no stations. The ends of the tunnel were sealed in the fall of 1861.
In March 1916, the FBI suspected German terrorists were making bombs in the tunnel, and broke through. They found nothing, installed an electric light, and resealed the tunnel. In the 1920s the tunnel was reportedly used for both mushroom growing and bootleg whiskey stills. In 1936, New York City police broke into the tunnel with jackhammers to look for the body of a hoodlum supposedly buried there. In 1941 the tunnel was again inspected by the federal Works Progress Administration to determine its structural strength. A few years later, it was once again opened, this time by the FBI, in an unsuccessful search for spies. During the late 1950s it was inspected by two rail historians, George Horn and Martin Schachne.
It fell into myth, but was rediscovered by the 18-year-old Robert "Bob" Diamond in 1981, who entered from a manhole at Atlantic and Court Street. It has been listed on the National Register of Historic Places since 1989.
Walt Whitman wrote of the tunnel: