Most postal historians know that ZIP codes were created by the U.S. Post Office Department in 1963 to make the delivery of increasing volumes of mail more efficient. These Zone Improvement Plan codes were never intended to be used for anything but mail delivery. They were created with the post office in mind, not neighborhoods or communities.
However, they’re frequently used as a proxy for neighborhoods for statistical purposes. For example, if you visit the U.S. Census Bureau’s American FactFinder, the search box prompts you to enter a state, county, city, town, or zip code.
A recent article from ThoughtCo. examines the use of ZIP codes as proxies for neighborhoods and the implications (along with some fun facts about ZIP codes).