26 zips
| Zip Code | City | Population ↓ |
|---|---|---|
| 6457 | Middletown | 47,030 |
| 6416 | Cromwell | 14,250 |
| 6413 | Clinton | 13,271 |
| 6424 | East Hampton | 12,372 |
| 6475 | Old Saybrook | 10,492 |
| 6371 | Old Lyme | 9,972 |
| 6480 | Portland | 9,409 |
| 6422 | Durham | 7,197 |
| 6498 | Westbrook | 6,829 |
| 6419 | Killingworth | 6,216 |
| 6441 | Higganum | 5,234 |
| 6423 | East Haddam | 4,887 |
| 6417 | Deep River | 4,445 |
| 6412 | Chester | 3,740 |
| 6426 | Essex | 3,377 |
| 6469 | Moodus | 3,377 |
| 6438 | Haddam | 3,079 |
| 6455 | Middlefield | 2,834 |
| 6442 | Ivoryton | 2,514 |
| 6481 | Rockfall | 1,406 |
| 6459 | Middletown | 1,122 |
| 6409 | Centerbrook | 863 |
| 6414 | Cobalt | 334 |
| 6456 | Middle Haddam | 271 |
| 6376 | South Lyme | 43 |
| 6439 | Hadlyme | 23 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 26 ZCTAs in Lower CT River Valley Planning Region, Connecticut (US Census).