ZIP Code 78578 — Port Isabel, TX
78578 is a standard (street delivery) ZIP code serving Port Isabel, Texas, in Cameron 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 78578 at a glance
| ZIP code | 78578 |
|---|---|
| Primary city | Port Isabel |
| State | Texas (TX) |
| County | Cameron FIPS 48061 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Chicago |
| Population | 10,016 |
| Coordinates | 26.053360, -97.310040 |
How ZIP+4 works in 78578
The four digits after the hyphen encode a delivery segment inside 78578. 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 78578 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 78578.
| ZIP | City | Distance |
|---|---|---|
| 78521 | Brownsville, TX | 7.1 mi |
| 78566 | Los Fresnos, TX | 8.9 mi |
| 78526 | Brownsville, TX | 9.5 mi |
| 78575 | Olmito, TX | 15 mi |
| 78597 | South Padre Island, TX | 15.1 mi |
| 78520 | Brownsville, TX | 16.1 mi |
| 78583 | Rio Hondo, TX | 18.6 mi |
| 78586 | San Benito, TX | 21.1 mi |
| 78550 | Harlingen, TX | 26 mi |
| 78567 | Los Indios, TX | 26.6 mi |
| 78552 | Harlingen, TX | 29.1 mi |
| 78535 | Combes, TX | 29.4 mi |
Questions about 78578
What is the ZIP+4 code for 78578?
78578 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 78578, you need to look up a specific street address to get them.
What city is 78578?
78578 is assigned to Port Isabel, Texas, in Cameron 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.