The secret history of the St. Louis Post Office and its amazing pneumatic tube

In 1905, the St. Louis post office built a two-mile pneumatic tube system to deliver mail between the train station and the post office. It was expensive to maintain ($17,000 per year per mile of tube) and ruined a lot of mail.

From Aimee Levitt's article in the Riverfront Times:

St. Louis's tubes ran a little less than two miles; by contrast, New York's system, the largest in the U.S., was 27 miles, not counting the tube that ran under the East River to Brooklyn. It was also the least efficient: Most of the time, the tubes, which were open from 4 a.m. to midnight six days a week, ran at only 26 percent capacity, except between 7 and 9 a.m. when the two big mail trains arrived. Then it was overwhelmed and the mail would be delayed for as long as 20 minutes. That was about five times as long as it took normally for the capsules to whiz their way from the train station to the main post office.

The tubes themselves were eight inches in diameter. The capsules were seven inches in diameter and 22 inches long; they could each hold about 600 letters. They didn't look much different from the capsules that are still used in banks. (Why mess with good technology?) Underground, they traveled at 30 miles per hour, propelled along by a system of fans and pumps that would either blow them forward or suck them backward.

Here's USPO's pro/con list of the system:


1. High rate of speed between stations for limited quantities of mail.

2. Freedom from surface congestion.

Limitation and disadvantages:

1. Only five pounds of mail could by carried in each container; and all classes of mail could not be carried.

2. The minimum time between dispatches is 15 seconds allowing only 20 pounds of letter mail each minute. Therefore, vehicle service would be required to carry mail during heavy volume times.

3. The inability to carry special delivery parcels due to the size of the carriers.

4. The relays at station are built in delays but they are unavoidable requiring all stations to be manned and open during operation.

5. The inability to dispatch between intermediate stations during continuous transmission between any two points.

6. Inability to dispatch to railroad companies without additional handling.

7. Complaints resulting from careless locking and accidental opening of container in transit causing damaged mail.

8. Dampness and oil damage to mail.

9. Service interruptions block an entire line.

10. Congestion from heavy mail volumes.

11. Equipment takes up rented building space.

12. Excessive costs.

By 1916 it was obsolete, replaced by mail trucks.

NewImage Too bad they shut it down. How cool would it be to get mail with a stamp that says: "Received through Pneumatic Tubes in bad order?"

The secret History of the St. Louis Post Office and its amazing pneumatic tube (Thanks, Keith Plocek!)


  1. I assume by “amazing” you mean “amazingly bad”, given the content of the rest of the article.  It sounds like the whole thing was poorly designed, annoying to use, expensive, and shut down fairly quickly.  

    It seems to me that design compromises up front (probably to save cost) ended up leaving them with a system that didn’t have capacity to handle the expected volume nor flexibility to  adapt to user demands. 

    1. I know!

      Just image if your graphic novels from Amazon showed up a month from now with a stamp saying “accidentally dropped from blimp by postal chimp!”. BUMMER!

  2. When I worked at Eaton’s in the Toronto Eaton Centre (the last version that turned into a Sears in 2002) and we had to do our nightly cash deposits via pneumatic tube. They wouldn’t let any sales associates know where the cash office was; no one knew where the tubes went, but every morning they’d come back with our float for the day.

    I’m sure they still use the tubes. Why change what ain’t broke.

  3. There was a time when tubes were considered to be a future means of transportation of persons. That time not only failed to arrive, but the idea was lost as well.

  4. We have a state-of-the-art P-tube system at the hospital where I work in the labs. We are a huge campus, and the lab building is across the street from the main hospital where most of the ORs are located. Every day many specimens are shot up, over, and down into our surgical pathology grossing station, where our faculty have to flash freeze it, micro-slice it, stain it, and assess it within 20 minutes – because the patient is still on the table.

Comments are closed.