Why ZIP codes have 5 numbers — and what they each mean

Purely History on Instagram: "The introduction of ZIP codes in 1963 marked a turning point in how mail was organized and delivered in the United States. Before then, postal workers relied heavily on local knowledge and often faced confusion with similar street names or growing urban areas. The new system, short for “Zone Improvement Plan,” gave every address a simple five-digit code that streamlined sorting and sped up delivery. What started as a practical fix for an overburdened postal system b