History of Post Office Technology

Postal Mechanization & Early Automation in the Post Office

Gehring Mail Distributing Machine test in Washington, DC, Post Office 1922
Gehring Mail Distributing Machine test in Washington, DC, Post Office 1922. USPO

At the turn of the 20th century, the Post Office Department relied entirely on antiquated mailhandling operations, such as the "pigeonhole" method of letter sorting, a holdover from colonial times. Although crude sorting machines were proposed by inventors of canceling machines in the early 1900s and tested in the 1920s, the Great Depression and World War II postponed widespread development of post office mechanization until the mid-1950s.

The Post Office Department then took major steps toward mechanization by initiating projects and awarding contracts for the development of a number of machines and technologies, including letter sorters, facer-cancelers, automatic address readers, parcel sorters, advanced tray conveyors, flat sorters, and letter mail coding and stamp-tagging technology.

Post Office Sorting Machines

As a result of this research, the first semi-automatic parcel sorting machine was introduced in Baltimore in 1956. A year later, a foreign-built multiposition letter sorting machine (MPLSM), the Transorma, was installed and tested for the first time in an American post office. The first American-built letter sorter, based on a 1,000-pocket machine originally adapted from a foreign design, was developed during the late 1950s. The first production contract was awarded to the Burroughs Corporation for 10 of these machines.
The machine was successfully tested in Detroit in 1959 and eventually became the backbone of letter-sorting operations during the 1960s and 70s.

Post Office Cancelers

In 1959, the Post Office Department also awarded its first volume order for mechanization to Pitney-Bowes, Inc., for the production of 75 Mark II facer-cancelers.
In 1984, more than 1,000 Mark II and M-36 facer-cancelers were in operation. By 1992, these machines were outdated and began to be replaced by advanced facer-canceler systems (AFCS) purchased from ElectroCom L.P. The AFCSs process more than 30,000 pieces of mail per hour, twice as fast as the M-36 facer-cancelers. AFCSs are more sophisticated too: they electronically identify and separate prebarcoded mail, handwritten letters, and machine-imprinted pieces for faster processing through automation.

Post Office Optical Character Reader

The Department's accelerated mechanization program began in the late 1960s and consisted of semi-automatic equipment such as the MPLSM, the single position letter sorting machine (SPLSM), and the facer-canceler. In November 1965, the Department put a high-speed optical character reader (OCR) into service in the Detroit Post Office. This first-generation machine was connected to an MPLSM frame and read the city/state/ ZIP Code line of typed addresses to sort letters to one of the 277 pockets. Each subsequent handling of the letter required that the address be read again.

Mechanization increased productivity. By the mid-1970s, however, it was clear that cheaper, more efficient methods and equipment were needed if the Postal Service was to offset rising costs associated with growing mail volume.

To reduce the number of mail piece handlings, the Postal Service began to develop an expanded ZIP Code in 1978.

The new code required new equipment. The Post Office entered the age of automation in September 1982 when the first computer-driven single-line optical character reader was installed in Los Angeles. The equipment required a letter to be read only once at the originating office by an OCR, which printed a barcode on the envelope. At the destinating office, a less expensive barcode sorter (BCS) sorted the mail by reading its barcode.

Following the introduction of the ZIP+4 code in 1983, the first delivery phase of the new OCR channel sorters and BCSs was completed by mid-1984.

Today, a new generation of equipment is changing the way mail flows and improving productivity. Multiline optical character readers (MLOCRs) read the entire address on an envelope, spray a barcode on the envelope, then sort it at the rate of more than nine per second. Wide area barcode readers can read a barcode virtually anywhere on a letter. Advanced facer-canceler systems face, cancel, and sort mail.

The remote barcoding system (RBCS) provides barcoding for handwritten script mail or mail that cannot be read by OCRs.


The ZIP+4 code reduced the number of times that a piece of mail had to be handled. It also shortened the time carriers spent casing their mail (placing it in order of delivery). First tested in 1991, the delivery point barcode, which represents an 11-digit ZIP Code, will virtually eliminate the need for carriers to case mail because mail will arrive in trays at the delivery post office sorted in "walk sequence." The MLOCR reads the barcode and address, then constructs a unique 11-digit delivery point barcode using the Postal Service's National Directory and the last two digits of the street address. Then barcode sorters put the mail in sequence for delivery.

Until now, most of the emphasis in automation has been processing machine-imprinted mail. Still, letter mail with addresses that were handwritten or not machine-readable had to be processed manually or by a letter sorting machine.

The RBCS now allows most of this mail to receive delivery point barcodes without being removed from the automated mailstream. When MLOCRs cannot read an address, they spray an identifying code on the back of the envelope. Operators at a data entry site, which may be far from the mail processing facility, read the address on a video screen and key a code that allows a computer to determine the ZIP Code information.

The results are transmitted back to a modified barcode sorter, which pulls the 11-digit ZIP Code information for that item, and sprays the correct barcode on the front of the envelope. The mail then can be sorted within the automated mailstream.

Handling Paper Flow

Letter mail represents approximately 70 percent of the Postal Service's total mail volume, so development of letter mail equipment has received the most attention. In addition to letter-mail processing, the Postal Service is taking steps to automate mail-forwarding systems and the processing of flats and parcels. The Postal Service also has accelerated installation of automated equipment in lobbies to serve customers better. The backbone of this effort is the integrated retail terminal (IRT), a computer that incorporates an electronic scale. It provides information to customers during a transaction and simplifies postal accounting by consolidating data. Postage validation imprinters have been attached to the IRTs to produce a self-sticking postage label that has a barcode for automated processing.

Competition and Change

In 1991, overall mail volume dropped for the first time in 15 years. The following year, volume rose only slightly, and the Postal Service narrowly avoided the first back-to-back declines in mail volume since the Great Depression.

Competition grew for every postal product.

The rise of fax machines, electronic communications, and other technologies offered alternatives for conveying bills, statements, and personal messages. Entrepreneurs and publishing companies set up alternate delivery networks in an attempt to hold down the costs of delivering magazines and newspapers. Many third-class mailers, finding their mailing budgets reduced and their postage rates increased higher than expected, began shifting some of their expenditures to other forms of advertising, including cable television and telemarketing. Private companies continued to dominate the market for the urgent delivery of mail and packages.

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Bellis, Mary. "History of Post Office Technology." ThoughtCo, Feb. 24, 2016, thoughtco.com/history-of-post-office-technology-1992139. Bellis, Mary. (2016, February 24). History of Post Office Technology. Retrieved from https://www.thoughtco.com/history-of-post-office-technology-1992139 Bellis, Mary. "History of Post Office Technology." ThoughtCo. https://www.thoughtco.com/history-of-post-office-technology-1992139 (accessed April 26, 2018).