uestion: What are the lowest and highest postal ZIP codes? (Asked by a curious, bashful fourth-grade student, in Greenwood)

Reply: The postal ZIP (Zoning Improvement Plan) codes are designed for more efficient mail delivery by having the designation indicated by the combination of numbers in the codes. One of the first countries to introduce ZIP codes was Germany in 1941. The United States adopted ZIP codes in 1963.

ZIP codes are numbered with the first of five digits representing a certain group of states, the second and third digits representing a group in that region or perhaps a large city, and the fourth and fifth digits representing a group of delivery addresses within a region. An extended ZIP + 4 code was introduced in 1983. Four digits determine a more precise location than the ZIP code alone. The “plus 4” might indicate a city block or an individual high-volume receiver. (Because of public resistance to more numbers, the “plus 4” is currently not required.)

In answer to the question, the lowest ZIP code, 01001, is for Agawam, Massachusetts; and the highest, 99950, is for Ketchikan, Alabama. There are two exceptions on the lower end, though. New York’s 00501 is strictly for the IRS center there, and 00601 is for Adjuntas, Puerto Rico. It is uncertain why it got a lower number when ZIP codes were assigned.

Starting in Maine, the numbers increase along the East Coast. From there, the numbers increase heading west and northward east of the Mississippi River, and northwest on to the West Coast, up to Alaska with 99950 for the Ketchikan post office.

The smallest post office is reported to be in Ochopee, Florida (ZIP 34141), measuring seven feet by eight feet. It was a shed used to store irrigation pipe for a tomato farm, and pressed into service when the general store containing the post office burned down. Serving fewer than 500 people, it appears to have escaped the post office closings and has become a tourist attraction.

The U.S. Postal Service delivers a lot of mail. Here are some statistics:

In fiscal year 2019, the USPS delivered 143 billion pieces of mail to 160 million delivery addresses and operated more than 31,000 post offices. It served more than 46 million rural addresses, and for much of rural America was often the only delivery option.

Forty-seven percent of the world’s card and letter mail volume is handled by the USPS. This includes delivery to the bottom of the Grand Canyon on mules.

C.P.S. (Curious Postscript): “Advertising is the art of convincing people to spend money they don’t have on things they don’t need.” — Will Rogers

Curious about something? Send your questions to Dr. Jerry D. Wilson, College of Science and Mathematics, Lander University, Greenwood, SC 29649, or e-mail jerry@curiosity-corner.net. Selected questions will appear in the Curiosity Corner. For Curiosity Corner background, go to curiosity-corner.net.