In the United States, a (Zone Improvement Plan) is a system of numerical codes used by the United States Postal Service ( USPS ) to facilitate efficient mail sorting and delivery. Launched in 1963, this five-digit system replaced the outdated method of relying on postal workers' personal knowledge of neighborhoods, which had become overwhelmed by a doubling of mail volume between 1940 and 1960.
Today, there are over 41,000 ZIP Codes utilized for mail, data, and logistics. The five-digit structure, running from 0 in the Northeast to 9 in the West, breaks down by region, section, and specific delivery point. Types include Standard, Unique (for high-volume entities), P.O. Box only, and Military. Introduced in 1983, the system allows for finer sorting, pinpointing specific blocks or buildings. Geographic Coding Structure 0-1: Northeast 1-2: Mid-Atlantic 2-3: Southeast 4-6: Midwest 6-7: Central/South 8-9: West zip code united states