The approximately 54 miles of tubes were in use from 1897 until 1953, linking most of the post offices in Manhattan, with a spur into Brooklyn. They enabled the postal system to move the mail at 30 miles per hour, irrespective of traffic or weather. The steel tubes (a double set, so the mail could move in both directions), 8 inches in interior diameter, were generally buried 4 to 6 feet beneath the surface, but they descended to 18 feet beneath Grand Central Station and, in some places, they ran underneath subway lines.

These tubes were used to carry steel cylinders, described as being like cannon shells with the warheads removed, 24 inches long and 8 inches in diameter. Inside dimensions were 22 inches with a 7-inch diameter. The canisters weighed 21 pounds apiece and could each hold about 400 to 500 letters. These cylinders, which spun or spiraled through the tubes, were propelled by a constant charge of compressed air, maintained at 3 to 8 pounds per square inch, supplied by a network of 11 power stations. While the system apparently could have generated sufficient air pressure to send the mail rocketing beneath the streets at a snappy 100 mph, the actual rate was kept to 30 mph so as to avoid disastrous encounters with the thousand or so turns, loops, and bends in the system.

The city's General Post Office, near Pennsylvania Station, served as the nerve center of the tube system. From there, a letter might travel up to Times Square, to Radio City, and so on past several stops at local post offices along the west side of Central Park. The route then passed through Harlem and down Manhattan's East Side, again with several intermediate stops, finally arriving at Grand Central Station, from whence a set of tubes led back to the main office. Alternatively, a missive might continue its journey past yet more stations farther downtown, past another nodal point at Church Street and on to Wall Street and Bowling Green, at the island's southern tip. From there, the tubes ran up the island again past Greenwich Village, back to the GPO. Mail for Brooklyn was sent out from Church St. along a branch line that was lifted over the Brooklyn Bridge.

Each container was labeled with the name of the station it was destined for or with a letter code. As the canister arrived at each intermediate station along its route, it popped out of its tube and, if heading on down the line, was placed in the outgoing tube; according to Post Office veterans, they came along every minute or so. On a full day, approximately 95,000 trips were made by these projectiles, containing as many as 5 million pieces of mail. From what one hears, apparently instances of cylinders being damaged or opening up in transit were utterly unheard of. In order to keep the tubes properly lubricated, dummy projectiles shaped like the others but perforated like a sieve and filled with oil were also sent out.

Rows of empty cylinders await their next trip through the pneumatic tube system at the General Post Office in Manhattan in 1951

Although the tubes made it easy to get the mail around the city in snow or rain or heat, gloom of night did stay these carriers—the system shut down at night, as well as on weekends and holidays. The tubes were built by the Tubular Dispatch Co., which had constructed a prototype system in Phila-delphia in 1893. (Boston, Chicago, and St. Louis also had such systems at one time, as did many cities in Europe; in fact, some post offices charged extra for the service.)

The actual system remained in private hands and was leased to what was then the Post Office Department, with the owner seeing to maintenance and the Post Office providing operating personnel. Small fans, set spinning by the wind in the tubes, showed that things were functioning correctly with no blockages. If the fan suddenly stopped, this meant something had gotten stuck, and the operators stepped up the air pressure behind the block and lowered it ahead to dislodge the jam. If that didn't work, workers had to dig up the tubes and break the jam by hand. On the Brooklyn extension, they had to crawl along a 12-inch catwalk attached to the bridge cables.

The systems in other cities were shut down in 1918, but intense lobbying from the contractors kept the tubes going in New York until 1953. By then, trucks had long since replaced horse-drawn vehicles for above-ground mail delivery, and they seemed far speedier and more efficient than this funny old technology. And yet, the old system could reliably get a letter from the GPO up to 125th St. in 20 minutes. Try to beat that in midday Manhattan traffic—never mind rush hour. Maybe people just expected faster service a century ago.

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