ZIP Code 81101 — Alamosa, CO
81101 is a standard (street delivery) ZIP code serving Alamosa, Colorado, in Alamosa County. To mail something here you only need these five digits — but the four-digit extension narrows delivery to a single point, and it is what USPS bulk postage discounts are priced on.
ZIP code 81101 at a glance
| ZIP code | 81101 |
|---|---|
| Primary city | Alamosa |
| State | Colorado (CO) |
| County | Alamosa FIPS 08003 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Denver |
| Population | 15,550 |
| Coordinates | 37.471970, -105.852430 |
How ZIP+4 works in 81101
The four digits after the hyphen encode a delivery segment inside 81101. In practice one segment usually means:
- One side of one block — odd numbers on a street between two cross streets
- A single large building, or one floor of it
- A group of PO boxes, sometimes a single box
- A single business that receives enough mail to warrant its own code
That is why 81101 has no single ZIP+4: two neighbors across the street from each other usually have different ones. Enter a street address above and we will return the exact nine-digit code along with the standardized USPS address format.
Nearby ZIP codes
Showing the closest twelve. See every ZIP code within 25 miles of 81101.
| ZIP | City | Distance |
|---|---|---|
| 81146 | Mosca, CO | 15.4 mi |
| 81123 | Blanca, CO | 16.4 mi |
| 81144 | Monte Vista, CO | 17.1 mi |
| 81136 | Hooper, CO | 17.6 mi |
| 81151 | Sanford, CO | 18.1 mi |
| 81124 | Capulin, CO | 19 mi |
| 81140 | La Jara, CO | 20.9 mi |
| 81141 | Manassa, CO | 21.5 mi |
| 81148 | Romeo, CO | 22 mi |
| 81125 | Center, CO | 26.6 mi |
| 81129 | Conejos, CO | 27 mi |
| 81133 | Fort Garland, CO | 28.8 mi |
Questions about 81101
What is the ZIP+4 code for 81101?
81101 is the five-digit ZIP code. The ZIP+4 adds four more digits that identify a specific delivery point — usually one side of a city block, a single building, or a group of PO boxes. Because those four digits change from address to address within 81101, you need to look up a specific street address to get them.
What city is 81101?
81101 is assigned to Alamosa, Colorado, in Alamosa County.
Do I need to use the ZIP+4?
It is optional for ordinary mail, but it speeds up sorting and it is required for most USPS bulk-mail postage discounts. Many address-verification and e-commerce systems also use ZIP+4 to confirm a delivery point exists.
Need thousands of these?
Upload a CSV and get ZIP+4, county, carrier route, and delivery-point data appended to every row — or call the API directly.