Eighty years ago, the U.S. Post Office Department introduced postal zone numbers in the 124 American cities shown here. These were the predecessors of the ZIP Code, introduced 20 years later in 1963.

The number was written after the city, but before the state. When the ZIP code was introduced, these zone numbers became the last two digits of the ZIP.

This list appeared in the October 1943 issue of National Radio News, which reminded readers to use add the code 9 between “Washington” and “D.C.” when mailing lessons and other items to the National Radio Institute.