© Mark Ollig
From 1889 to 1893, John Wanamaker served as US Postmaster General and strongly advocated pneumatic mail delivery.
In 1892, Congress appropriated $10,000 to Philadelphia to build a two-and-a-half-mile network of eight-inch pneumatic mail tubes beneath the city streets.
In 1893, the Philadelphia Post Office became the first US high-speed delivery mail transport system.
This system used air pressure to propel a cylindrical capsule or container (sometimes referred to as a carrier) through a network of tubes between post office substations and the main post office.
Capsules were made of gutta-percha (similar to rubber but harder and less elastic), leather, wood, durable fibers, steel, and a mostly brass shell casing.
The Philadelphia Times wrote the new pneumatic tubes were a “conspicuous success” Feb. 19, 1893.
“Postmaster General Wanamaker and Philadelphia Postmaster Field inaugurated the pneumatic tube, and after dedicating it to piety and patriotism by the Bible and the flag [included inside a container], sent mail matter through it with such speed as to obliterate time,” the article said.
The sound made by a capsule rushing through the tubes was described as “whoosh!”
The capsules varied in diameter depending on the size of the tubes, typically six to seven inches for the eight-inch tubes and around five inches for the six-inch tubes.
To return capsules, the system removed air from the tubes, creating lower pressure that pulled them back, allowing two-way travel within the same tubes.
The pneumatic tube system used electric motors, rotary blowers, and air compressors to create air pressure (3 to 8 psi) that pushed capsules through the tubes.
Although the capsules could reach up to 100 miles per hour, the turns in the tube network limited their average speed to 30 to 35 mph. Reaching their destination, the mail containers emptied onto a cloth-aproned catch.
A majority of the pneumatic tube network was located underground and within buildings.
The tubes usually connected with each other using flanging, which widened the tube ends, which were secured with bolts and a gasket to the next tube for an airtight connection.
Lead-based soldering was used for junction points where tubes branched off or changed direction.
Due to high costs and fabrication challenges, steel wasn’t commonly used for pneumatic tube construction until the early 1900s.
“Mail Matter Cut in Pneumatic Tubes” was the Philadelphia Inquirer newspaper headline March 5, 1893, describing “an accident in the service that destroyed many letters.”
The article mentioned a “serious hitch” that temporarily disrupted mail delivery between postal substations and the post office’s pneumatic tube system.
The lid of a mail carrier capsule wasn’t properly fastened. As it traveled through the tube system, it detached, spilling mail parcels that were then shredded by another speeding capsule, “cutting them to pieces,” as the newspaper put it.
The Pneumatic Transit Company operated the Philadelphia mail tube system.
The Philadelphia Inquirer published “The Pneumatic Tubes Facilitate the Handling of Post Office Business” on May 2, 1893. The article stated that the pneumatic tube between the main post office and the East Chestnut Street substation was operational, and that the new system would deliver mail much faster. It also noted previous problems, likely referring to the “serious hitch” described in the March 5 article.
New York City started using a network of pneumatic mail tubes Oct. 7, 1897, mostly made of cast iron with an inside diameter of eight and one-eighth inches buried four to six feet below the ground.
A capsule carrier pierced with holes and filled with oil would occasionally be sent through the tubes to keep them lubricated.
Due to the fast speed of the mail carriers traveling through the pneumatic tubes, the New York City postal workers operating them were nicknamed “rocketeers.”
In time, New York City was using 27 miles of tubes connecting 23 post offices.
Pneumatic mail tube systems began in Boston (1897), Brooklyn (1898), St. Louis (1904), and Chicago (1898).
The 1909 US Government Printing Office report “Investigations as to Pneumatic-Tube Service for the Mails” notes, “The contract speed of 30 miles an hour between stations is in strong contrast with the contract rate for mail-wagon service, which would range from three to five miles per hour.”
The same report states the US Congress’ post-office appropriation bill for the fiscal year ended June 30, 1909, provided “for the transmission of mail by pneumatic tubes or other similar devices, $1,000,000.”
By 1915, six US cities used pneumatic tubes: New York, Brooklyn, Boston, Philadelphia, Chicago, and St. Louis, according to the United States Postal System.
In the years that followed, more economical mail transport methods led to the decline in use of the mail tube system.
In late 1953, the US Post Office Department ended its use of tube systems for mail delivery, citing tube capacity limits due to expanded mail volume, high costs, and maintenance.
I found no record of Minnesota ever having used a pneumatic tube system for delivering the US mail.
Today, pneumatic tubes are being used in hospitals, manufacturing facilities, industrial facilities, and bank drive-throughs.
The pharmacy where I pick up my prescriptions has a drive-through pneumatic tube system.
