Clerks sort mail in the cramped interior of a Railway Post Office (RPO). RPO interiors typically ranged from 15 to 60 feet long and were about 9 feet wide. Tight-knit crews of up to 20 men worked in the larger cars, racing the clock to sort mail in time for dispatch to the stations en route. “Working the mail” consisted of sorting letters into “pigeon hole” distribution cases and tossing mail accurately into labeled pouches, correctly routed to as many as 5,000 destinations. Whenever one man finished his work he often pitched in to help another. Clerks had to memorize complex distribution schemes and studied and practiced continuously in order to pass regularly-scheduled examinations.
collection of United States Postal Service