The US Postal Service introduced ZIP codes
On this day · 1 July 1963
On a single summer day in 1963, every American address quietly grew five digits longer to help mail move faster.
On July 1, 1963, the US Post Office Department rolled out the five-digit ZIP Code, short for Zone Improvement Plan. The new code was part of a broader push to speed mail delivery at a time when annual volume had ballooned past 63 billion pieces, far more than the old hand-sorting system could comfortably handle.
The idea built on decades of work. Postal inspector Robert Moon proposed the first three digits, which identify a region and a central sorting facility, as early as the 1940s; a colleague added the final two digits to pinpoint a specific post office or delivery area. Paired with new automated sorting machines, the codes let mail be routed with far less manual reading of addresses.
To win over a skeptical public, the department launched an energetic campaign fronted by the cartoon mascot Mr. ZIP, who appeared on everything from posters to lunchboxes.
Five small digits reshaped how an entire nation’s mail found its way home.
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