The user searching for ZIP Code 00001 is looking for the location associated with this specific postal code.
The direct and authoritative answer is that 00001 is not a currently active, recognized, or assigned ZIP Code by the United States Postal Service (USPS) for general mail delivery. While it exists in some data sets as the numerical start of the US postal range, it does not correspond to a specific city or town where you can send a letter.
This article clarifies the status of the 00001 code, reveals the true lowest-numbered ZIP Code in use, and explains how US ZIP Code zones are structured.
Status of ZIP Code 00001
The ZIP Code system is a complex, ordered structure managed by the USPS. Codes starting with ‘0’ are geographically located in the Northeast and territories of the United States.
| Detail | Information |
| Status: | Not in Use / Invalid. |
| Geographic Location: | None. Cannot be used for official mail delivery. |
| Why it Appears in Data: | Some database lists include 00001 as the theoretical numerical minimum of the 5-digit range (00001 through 99950), but it is not a working postal code. |
| Region (If Assigned): | Any code starting with ‘0’ falls into the area that includes New England, New Jersey, Puerto Rico, and the U.S. Virgin Islands. |
The True Lowest Assigned ZIP Code
The actual lowest 5-digit ZIP Code currently in use in the United States is:
- ZIP Code: 00501
- Location: Holtsville, New York
- Designation: This unique code is reserved exclusively for the Internal Revenue Service (IRS) Center located in Holtsville, New York.
The highest ZIP Code in use is 99950, which is designated for a remote area in Ketchikan, Alaska.
How US ZIP Codes Are Structured
The five digits of a US ZIP Code are assigned based on a geographic hierarchy, moving from east to west.
- The First Digit (Broad Geographic Area)
The first digit of a ZIP Code designates a large group of US states. Since the query “00001” starts with a zero, we know that if it were valid, it would fall in the following region:
| First Digit | Geographic Area | States/Territories Included |
| 0 | Northeast / Territories | Maine, Vermont, New Hampshire, Massachusetts, Rhode Island, Connecticut, New Jersey, Puerto Rico, and the U.S. Virgin Islands. |
| 1 | East | Delaware, New York, Pennsylvania |
| 2 | South | Virginia, Maryland, North Carolina, South Carolina, West Virginia, Washington D.C. |
| 9 | West | California, Oregon, Washington, Alaska, Hawaii |
- The Second and Third Digits (Sectional Center Facility)
The second and third digits represent the Sectional Center Facility (SCF), which is the regional mail processing hub through which mail is sorted. Codes closer to 000 (like 005xx) often represent specific, high-volume recipients or special areas rather than typical towns.
- The Fourth and Fifth Digits (Delivery Area)
The final two digits designate the Post Office or Delivery Area within the SCF’s region. This could be a local post office, a specific route, or a large building, as is the case with the IRS at 00501.
Frequently Asked Questions (FAQ)
Is 00001 a valid ZIP Code for online forms?
No. Most website forms that validate addresses against the official USPS database will reject 00001 as invalid. If a form requires a 5-digit code, you must enter one of the currently recognized codes in the USPS system, such as 00501 (for the IRS) or any general code like 10001 (New York, NY).
If 00001 is not used, why are all ZIP Codes 5 digits long?
The ZIP Code system was launched in 1963 and uses the 5-digit format to efficiently route mail. The format allows for almost 100,000 unique codes (00000 to 99999). Codes like 00001 are simply left unassigned for future use, reserved, or avoided for historical/technical reasons.
Is the ZIP Code 00501 for the entire town of Holtsville, NY?
No. The area of Holtsville, New York, is largely served by the standard 11742 ZIP Code. The code 00501 is a unique, non-geographic code assigned exclusively to the Internal Revenue Service (IRS) mail processing facility in that town.
Conclusion
The search for the location of ZIP Code 00001 leads to the important clarification that it is not an active or valid postal code for any US location. The smallest assigned code is 00501, reserved for the IRS in New York. For reliable mail delivery and accurate online form completion, always use one of the over 41,000 codes currently maintained in the official United States Postal Service database.
