During the 1870s and ’80s, inventors filed more than a dozen patent applications in the United States for electrical improvements to letter boxes. But why did mailboxes and letter slots, surely among the simplest mechanical devices, have to be electrified? It was primarily a matter of convenience, for people who wanted to know exactly when the mail had arrived and didn’t want to waste time checking.
Free home delivery of the mail had begun in the United States in 1863, but mailboxes were not yet standard. Instead, a postman would knock on the door (perhaps with a handheld wooden knocker), wait for someone to answer, and then hand over the mail. If no one was home, the carrier returned later or the next day. Although this created great trust in the system, it wasn’t very efficient. In 1909, postal officials calculated that on a typical day, carriers made 360 stops and spent an average of 15 seconds per delivery, or an hour and a half a day, simply waiting.
Beginning in the 1880s, the U.S. Post Office Department began encouraging people to install a mailbox or letter slot, although they didn’t become a requirement until 1923. (For a nice concise history of the U.S. Postal Service, see The United States Postal Service: An American History 1775–2006 [PDF].)
And so, many of the early patents for electrical indicators for letter boxes tried to replace or augment the postman’s knock. Inventor Henry R. David thought that large office and apartment buildings in cities had a particular problem. His 1875 U.S. patent [PDF] detailed a system of circuits that would inform people in far-flung corners of the building that mail was waiting for them at the main entrance.
Many of the electric letter boxes, including the device that William H. Rodgers described in an 1879 patent [PDF], worked by closing a battery-powered circuit when the postman deposited letters in the box. The circuit would ring a bell inside the house. Sometimes, though, the weight of a single letter wasn’t enough to engage the circuit, as Rodgers noted in another patent that same year [PDF]. The inventor’s improved design engaged the circuit when the postman opened the box. The circuit, after ringing the distant bell, stayed locked in the on position, until the box was reopened. Obviously, Rodgers never imagined that pranksters might repeatedly open and close the box to set off the mail bell.
Charles H. Carter did spot this problem, claiming in his 1880 patent [PDF] that owners of such mailboxes were inconvenienced by “any person raising the lid or inserting any unimportant circular.” In his design, the postman would sound an alarm by means of a skeleton key. Unfortunately for Carter, the Post Office Department issued standards that required mailboxes to, among other things, allow carriers to withdraw and deposit mail “without delay.” A design that required a separate key to indicate delivery was unlikely to be approved.
Carter applied for another mailbox patent that introduced a visual indicator [PDF]. Once a letter closed the circuit, a configuration of electromagnets would expose a flap labeled “mail.” Carter suggested that the flap could also have numbers or other visual cues to call attention to the change in status.
Despite the many patented designs for electric mailboxes, Alice H. Ewing clearly believed there was room for improvement when she applied for a U.S. patent in 1915. Patent 1,228,193 [PDF], issued to Ewing two years later, opted not for a bell or flap but for an electric light. A convenient push button next to the light would reset the circuit.
A great benefit of reviewing the history of invention through patents is that all of the technical details are well documented. But a century or more after the fact, historians often struggle to determine whether a particular idea was ever put into production, unless there is additional supporting evidence. In the case of Ephraim E. Weaver’s 1885 patent [PDF], a surviving mailbox does exist [top photo], at the Smithsonian National Postal Museum, in Washington, D.C. (Full disclosure: I used to work as a curator at the museum.) Weaver’s patent was for an indicator for items that didn’t fit in the box and thus didn’t trigger the bell. His electric mailbox came with a key that the delivery person could use to close the circuit and ring the bell.
The box in the museum’s collection doesn’t conform exactly to its patent drawing. Curator Lynn Heidelbaugh reports that it has no external handle like the one labeled “E” in the patent drawing below:
For now, the inconsistencies will remain a mystery because this particular mailbox was found in the museum’s collections without any associated information. Curators don’t know where it was used or for how long, or whether its owners found it useful. Just as there are limits to the information that can be gleaned from a patent, physical evidence doesn’t always want to give up its story either.
Although electric mailboxes never became mainstream, the idea has recently resurfaced as a playful exercise to teach basic circuit design. For example, Electronics Hub, a website that posts DIY projects and tutorials, has an Electronic Letter Box Project Circuit that uses blinking LEDs as the indicator. Instead of physically closing a circuit, as all of the 19th-century inventions did, this one uses an LDR (light dependent resistor). When a letter blocks the photoresistor, the circuit registers that you have mail.
SparkFun, a company dedicated to electronics literacy, upped the ante with an interactive letterbox for Valentine’s Day cards. It relies on an infrared transmitter to count the number of letters that pass through the mail slot. Upload a bit of code to your Arduino, and the LED counter shows how many letters have been received.
Meanwhile, the U.S. Postal Service has introduced Informed Delivery, which sends customers scanned images of the letters they can soon expect along with notifications of packages. Multiple people at the same address can sign up for individual notifications. The service isn’t yet available everywhere, and it’s not always 100 percent accurate. Critics of the system say it poses potential security risks.
Personally, I still love walking down my driveway to check my mailbox. And on sunny days, when I am looking to procrastinate, I have no problem making that trip more than once. Compare that to my first email account, which currently has over 106,860 unread messages. My work email inbox is marginally better, with 6,067 unread messages. Long ago I turned off any digital indicator announcing the arrival of a new email. There is simply too much. In the prescient patent of Charles Carter, I too prefer not to be annoyed by all those “unimportant circulars.”
An abridged version of this article appears in the June 2018 print issue as “A Better Mailbox.”
Part of a continuing series looking at photographs of historical artifacts that embrace the boundless potential of technology.
About the Author
Allison Marsh is an associate professor of history at the University of South Carolina and codirector of the Ann Johnson Institute for Science, Technology & Society there.