The Railway Post Office: A Ride Through History

The Railway Post Office (RPO) offers a compelling view into an era when transportation and communication were intimately interwoven, highlighting how the railway system was central to the development of modern mail delivery services. Operating in the United States from the mid-19th to the mid-20th century, the RPO was not merely a mail-carrying service but a moving post office that sorted mail en route to its destination.

Origins and Development

The RPO officially began in 1862 when George B. Armstrong, the Assistant Postmaster of Chicago, formalized the concept of a fully functional post office on wheels. However, its roots go back further to 1832, with the unofficial carriage of mail on the locomotives of the new railways. By the 1860s, the sheer volume of mail necessitated an innovative approach to sorting and delivery, leading to the establishment of the RPO.

The railway mail car, also known as an RPO car, was the operational hub of this service. The interior of the car was designed to efficiently sort mail while traveling at high speed. Adjustable pigeon-hole style sorting racks, worktables, and cancellation machines were all part of the railway mail clerk’s workspace. Clerks had to memorize vast amounts of data about the mail delivery system, including the details of sorting schemes, train schedules, and the geography of the routes they covered.

Impact and Importance

The RPO transformed mail delivery in the U.S., significantly reducing the time it took for a letter or parcel to travel from one place to another. By moving the sorting process onto the train, the RPO eliminated delays that occurred when mail was sorted at stationary post offices. This was particularly important for the growing country, as it provided a reliable and efficient method of communication between cities, towns, and even rural areas, bridging the vast American landscapes.

The RPO also played an integral role in the expansion of the railway system. As railway lines grew to serve the RPO, they also increased connectivity between various parts of the country, fostering trade and migration. Many towns and cities grew and developed along these railway lines, contributing to the country’s westward expansion.

Decline and Discontinuation

Despite its significant contributions, the RPO began to decline in the mid-20th century. The rise of aeronautic mail transport, increased use of personal vehicles, and improved road infrastructure collectively began to eclipse the efficiency of railway mail. The decline was cemented with the introduction of ZIP codes in the 1960s, which streamlined mail sorting in stationary offices and rendered the moving sorting system less necessary.

The last official RPO run occurred on June 30, 1977, between New York and Washington, D.C., marking the end of an era.


Today, the legacy of the RPO is preserved in railway museums across the United States. Restored RPO cars and exhibits provide a glimpse into this unique chapter of American history. While the RPO may no longer be in operation, its impact on the development of the modern postal service and the country as a whole cannot be overstated.


The Railway Post Office was an extraordinary innovation in its time, showcasing the remarkable adaptation of technology and transportation to meet the evolving needs of society. As we navigate through the 21st century, the spirit of ingenuity embodied by the RPO continues to inspire advances in communication and transport systems, reminding us that progress is often a journey, not a destination.

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