In February 1870, New Yorkers paid 25 cents apiece to ride a secret subway. They descended beneath Devlin's clothing store at Broadway and Warren Street into a marble-walled waiting room with a grand piano, a fountain stocked with goldfish, and a frescoed ceiling lit by zircon lamps. Then they boarded a single cylindrical car and were blown through a brick tunnel by a 50-ton fan named the "Western Tornado."

This was Alfred Ely Beach's pneumatic subway — and it existed because he had built it illegally.

Beach was the editor of Scientific American and a serial inventor (he held an early patent on the typewriter). In the 1860s, New York's streets were a hellscape of horse traffic and manure, and several proposals for elevated railways were circulating. Beach was convinced the answer was underground and pneumatic — but Boss Tweed's Tammany Hall machine controlled all transit franchises, and Tweed had a financial interest in elevated rail. Beach knew an aboveboard application would be killed.

So he applied for a permit to build a small pneumatic mail tube. Then he secretly widened the plans. Working only at night, his crew dug a 312-foot tunnel under Broadway using a hydraulic shield Beach had designed himself — an ancestor of the tunnel boring machines that dig modern subways. The dirt was carted out in the dark. Tweed found out only when Beach unveiled the finished thing to the press.

The public loved it. Over 400,000 people rode the demonstration line in its first year. But Beach needed legislative approval to extend the tunnel into a real transit system, and Tweed blocked every bill. By the time Tweed fell in 1873 (jailed for corruption), the Panic of 1873 had wiped out Beach's investors. The tunnel was sealed up and forgotten.

It stayed forgotten for 39 years. In 1912, workers excavating for the BMT Broadway subway broke through a wall and found Beach's tunnel essentially intact — the wooden car still sitting on its rails, the fountain still in the waiting room, the piano rotted but recognizable. The City Hall station of today's R/W line sits roughly where Beach's parlor was.

A few things worth knowing:

• Pneumatic transit wasn't crank science. London's Crystal Palace pneumatic railway ran passenger service in 1864, and pneumatic mail systems hauled letters under Paris, Berlin, Prague, and New York for decades — Prague's still partially operates as a heritage system.
• Beach's tunnel shield is the direct conceptual ancestor of the machines that dug the Channel Tunnel and the Second Avenue Subway.
• The fan reversed direction at the end of each run — it sucked the car back rather than pushing it. The car was essentially a giant ping-pong ball in a tube.

The wildest part isn't the technology. It's that the entire first subway in the most-watched city in America was built in secret, beneath a clothing store, by a magazine editor.