Postal Mechanization and Early Automation

At the turn of the 20th century, despite growing mail volume and limited work space, the Post Office Department relied on antiquated mailhandling methods, such as the pigeonhole method 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 mechanization until the mid-1950s.

In 1956, the Post Office Department began intense research on coding systems used in 13 other countries and began to work with the U.S. Bureau of Standards and the Rabinow Engineering Company, among others, to develop a system best suited to U.S. postal needs. They examined codes for extracting information and the memory core needed by automated letter sorting machines.

The Post Office Department also initiated projects and awarded contracts to develop 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 techniques.

The first semiautomatic 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 adapted from a foreign design, was developed during the late 1950s. The first production contract was awarded to the Burroughs Corporation for ten machines. The machine was successfully tested in Detroit in 1959 and eventually became the backbone of letter sorting operations during the 1960s and 70s. 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.

The Department’s accelerated mechanization program began in the late 1960s and consisted of semiautomatic 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 277 pockets. Subsequent handlings 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. By 1972, the Postal Service had begun to examine how to sort mail in the order a letter carrier would deliver it. In 1978, the Postal Service also began to develop an expanded ZIP Code to reduce the number of mailpiece handlings.

The new code required new equipment. In September 1982, the first computer-driven, single-line OCR 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 destination Post Office, a less expensive barcode sorter (BCS) sorted the mail by reading its barcode.

The Postal Service had begun to develop an expanded ZIP Code of
four add-on digits that would speed processing when coupled with new automation equipment capable of sorting mail to small geographic segments, such as city blocks or a single building. Following the introduction of this ZIP+4 code in 1983, the first delivery phase of the new single-line OCR channel sorters and BCSs was completed by mid-1984. By the end of 1984, 252 OCRs were installed in 118 major mail processing centers across the country and were processing an average of 6,200 pieces of mail per workhour — a substantial increase compared to the 1,750 pieces per work hour processed by MPLSMs.