The Cobble Hill Tunnel was New York’s first subterranean rail tunnel but today it lies abandoned under the streets of Brooklyn. Many of those living above don’t even know it exists.
The tunnel is also known as the Atlantic Avenue Tunnel and was part of the Long Island Railroad. It was 767 metres and is the oldest railway tunnel in North America. It was built as part of the Brooklyn and Jamaica Railway in 1844 and the line ran as far as the South Ferry on Atlantic Street. From there, the ferry would take people from Brooklyn to Manhattan.
Construction on the open cut began in May 1844 and was opened on 3 December 1844. The cut was roofed over in 1849, converting it into a tunnel 17 feet (5.2 metres) high. Although claimed as the world’s first subway tunnel, Cobble Hill Tunnel had no stations and was only used for through traffic. The Brooklyn and Jamaica Railway later rebranded as the Long Island Railroad.
The Cobble Hill Tunnel was used as part of the main New York to Boston rail route and was the main means of accessing Long Island from Manhattan. The railroad connected Lower Manhattan via the South Ferry to Greenport on the North Fork of Long Island, where a ferry connected to Stonington, Connecticut. A rail link continued from there to Boston. This route was made redundant in 1848 when the New York and New Haven Railroad Line was completed through Connecticut, providing a direct, faster rail connection from New York City to Boston. The Cobble Hill Tunnel and the Long Island Railroad remained the primary means of access to most of central Long Island from Manhattan and New York City.
In 1861, the City of Brooklyn banned all railroad locomotives from within the city limits and both ends of the tunnel were sealed up. The Cobble Hill Tunnel was largely forgotten about, confined to history beneath the ever expanding borough.
The tunnel was searched in March 1916 when the Bureau of Investigation believed that German terrorists were using it to make bombs. They broke through the roof with jackhammers but found nothing. They resealed it after installing an electric light. There were rumours in the 1920s that it was being used to bootleg whiskey during the prohibition era but this was never properly investigated. In 1936, the New York City Police Department tried to enter the tunnel to find the body of a murder victim they believed to be buried there but were unable to get inside. The tunnel was opened by the FBI again in the 1940s in another unsuccessful search for spies.
The Cobble Hill Tunnel was lost from public notice until 1980 when 20-year-old Robert Diamond rediscovered it. He entered a manhole on Atlantic Avenue, crawled for 70 feet (21 m) underground through a filled-in section of tunnel less than two feet high and located the wall that sealed off the tunnel. A Brooklyn Union Gas Co. engineering team helped him break through the wall. He began leading tours of the tunnel in 1982. He did so until 17 December 2010 when the Department of Transportation terminated his contract on safety grounds. Robert Diamond was also involved in the founding of the Brooklyn Historic Railway Association which maintained a number of old trolleys in the Red Hook area of Brooklyn. The Cobble Hill Tunnel was listed on the National Register of Historic Places in 1989.