Just over fifty years ago, a five-digit number revolutionized mail delivery in the United States.

The nearly 42,000 Zone Improvement Plan (ZIP) codes we use today were officially launched on July 1, 1963 at a time when the amount of mail had increased dramatically with the influx of business mail like bills, checks and advertisements.

At first glance, a series of government-assigned numbers intended to simplify mail delivery may seem far from interesting, but believe it or not, ZIP codes actually have quite the fascinating history.

ZIP Code History

Mr. Zip on stamps. Wikimedia Commons

1. To encourage people to use the newly launched ZIP codes, the Post Office Department — the U.S. Postal Service’s predecessor — created Mr. Zip, a cartoon mail carrier that appeared on stamps and posters. Howard Wilcox, the son of a letter carrier, designed the original Mr. Zip, but Post Office Department artist Joe Lawrence refined the illustration before unveiling the character at a postmasters’ convention.

2. Unique ZIP codes are reserved for government agencies, businesses, schools and buildings that receive particularly large volumes of mail. For example, the CIA (20505), Sears Tower (60606), Dodger Stadium (90090) and LaGuardia Airport (11371) all have their very own ZIP codes.

3. Not only does the White House have its own ZIP code (20500), but it also has its very own secret ZIP code for the president and first family to receive mail.

4. In 2005, the ZIP code 77230 was assigned for mail delivery to victims of Hurricane Katrina who were housed at the Houston Astrodome.

Smokey Bear reading mail. U.S. Department of Agriculture/flickr

5. Smokey Bear, the U.S. Forest Service’s mascot, was assigned his own ZIP code (20252) in 1964 because he received so much fan mail.

6. The USPS revoked Centralia, Pennsylvania’s ZIP code (17927) in 1992 long after the town had mostly been abandoned. A coal fire that began in 1962 has spread throughout mines beneath the town and continues to burn today. The few residents that remain must use the ZIP code that belongs to the nearby borough of Ashland (17921).

Unique ZIP Codes

7. The easiest ZIP codes to remember belong to Newton Falls, Ohio, (44444) and General Electric in Schenectady, New York (12345).

8. The lowest ZIP code (00501) is a unique code for the IRS in Holtsville, New York. The highest one (99950) belongs to Ketchikan, Alaska.

9. Wayne, New Jersey (07470) and Jacksonville, Florida, (32223) both boast palindromic ZIP codes.

10. Your ZIP code says something about you. Type in your ZIP code here, and Esri, a geographic-information firm, will provide you with an interesting breakdown of information about your area. Is your ZIP code full of Metro Renters who shop at Whole Foods and take yoga or Middleburg married couples that enjoy baseball and country music? Find out.