First three digits · Iowa
ZIP Codes Starting with
57 ZIP codes start with 504, sorted at the Waterloo, IA (SCF 506) sectional center (USPS labeling list L005, effective October 1, 2026) in Iowa: 55 residential ZIP codes across 10 counties and 2 PO Box or single-organization codes (Census 2020 ZCTAs and GeoNames postal codes, October 2026).
What do the digits 504 mean?
The first digit, 5, is one of ten national areas (Iowa, Minnesota, Montana, North Dakota, South Dakota and Wisconsin). The first three, 504, route mail to a sectional center: USPS labeling list L005 (effective October 1, 2026) sends letters for 504 to the Waterloo, IA (SCF 506) facility. The last two digits pick the delivery area. By residents, the largest town names among the 504 ZIP codes are Mason City, Clear Lake, Forest City, Hampton, Osage and Garner.
The same facility sorts 4 prefixes, 165 ZIP codes in all: 504, 506, 507, 521.
Where are the 504 ZIP codes?
Source: U.S. Census Bureau, 2020 ZCTA cartographic boundaries; ACS 2020-2024 5-year estimates (B19013).
All ZIP codes starting with 504
| County | ||||||
|---|---|---|---|---|---|---|
| 50401 | Mason City | Cerro Gordo County | 28,703 | 194 | $66k | $147k |
| 50402 | Mason City | Cerro Gordo County | PO Box or unique | – | – | – |
| 50420 | Alexander | Franklin County | 473 | 10 | $76k | $102k |
| 50421 | Belmond | Wright County | 3,168 | 34 | $64k | $136k |
| 50423 | Britt | Hancock County | 2,291 | 16 | $73k | $119k |
| 50424 | Buffalo Center | Winnebago County | 1,441 | 10 | $59k | $115k |
| 50426 | Carpenter | Mitchell County | 81 | 231 | $74k | $64k |
| 50427 | Chapin | Franklin County | 137 | 2,015 | $73k | $94k |
| 50428 | Clear Lake | Cerro Gordo County | 9,071 | 77 | $81k | $283k |
| 50430 | Corwith | Hancock County | 520 | 8 | $59k | $76k |
| 50431 | Coulter | Franklin County | 228 | 305 | $63k | $90k |
| 50432 | Crystal Lake | Hancock County | 283 | 651 | $67k | $100k |
| 50433 | Dougherty | Cerro Gordo County | 157 | 3 | $69k | $86k |
| 50434 | Fertile | Worth County | 396 | 39 | – | – |
| 50435 | Floyd | Floyd County | 713 | 18 | $71k | $146k |
| 50436 | Forest City | Winnebago County | 5,771 | 43 | $75k | $168k |
| 50438 | Garner | Hancock County | 3,995 | 31 | $70k | $198k |
| 50439 | Goodell | Hancock County | 454 | 14 | $94k | $80k |
| 50440 | Grafton | Worth County | 361 | 12 | $76k | $123k |
| 50441 | Hampton | Franklin County | 5,450 | 37 | $50k | $127k |
| 50444 | Hanlontown | Worth County | 394 | 19 | $78k | $147k |
| 50446 | Joice | Worth County | 476 | 12 | $107k | $154k |
| 50447 | Kanawha | Hancock County | 1,145 | 11 | $76k | $87k |
| 50448 | Kensett | Worth County | 620 | 10 | $62k | $123k |
| 50449 | Klemme | Hancock County | 785 | 19 | $60k | $95k |
| 50450 | Lake Mills | Winnebago County | 2,952 | 35 | $76k | $158k |
| 50451 | Lakota | Kossuth County | 432 | 7 | $54k | $53k |
| 50452 | Latimer | Franklin County | 946 | 20 | $66k | $120k |
| 50453 | Leland | Winnebago County | 537 | 12 | $78k | $154k |
| 50454 | Little Cedar | Mitchell County | 229 | 16 | $64k | – |
| 50455 | McIntire | Mitchell County | 201 | 6 | $42k | $93k |
| 50456 | Manly | Worth County | 1,699 | 34 | $81k | $125k |
| 50457 | Meservey | Hancock County | 463 | 14 | $47k | $91k |
| 50458 | Nora Springs | Floyd County | 2,094 | 30 | $100k | $158k |
| 50459 | Northwood | Worth County | 3,045 | 21 | $72k | $150k |
| 50460 | Orchard | Mitchell County | 688 | 19 | $77k | – |
| 50461 | Osage | Mitchell County | 5,228 | 29 | $69k | $180k |
| 50464 | Plymouth | Cerro Gordo County | 694 | 28 | $92k | $197k |
| 50465 | Rake | Winnebago County | 190 | 57 | $42k | $49k |
| 50466 | Riceville | Howard County | 1,972 | 14 | $57k | $210k |
| 50467 | Rock Falls | Cerro Gordo County | 63 | 56 | $64k | $150k |
| 50468 | Rockford | Floyd County | 1,617 | 16 | $73k | $174k |
| 50469 | Rockwell | Cerro Gordo County | 1,527 | 18 | $71k | $212k |
| 50470 | Rowan | Wright County | 287 | 12 | $73k | $69k |
| 50471 | Rudd | Floyd County | 740 | 17 | $94k | $133k |
| 50472 | Saint Ansgar | Mitchell County | 2,560 | 21 | $94k | $204k |
| 50473 | Scarville | Winnebago County | 219 | 6 | $50k | $141k |
| 50475 | Sheffield | Franklin County | 1,446 | 15 | $71k | $165k |
| 50476 | Stacyville | Mitchell County | 706 | 18 | $62k | $120k |
| 50477 | Swaledale | Cerro Gordo County | 250 | 13 | $52k | $83k |
| 50478 | Thompson | Winnebago County | 737 | 10 | $49k | $93k |
| 50479 | Thornton | Cerro Gordo County | 655 | 11 | $69k | $121k |
| 50480 | Titonka | Kossuth County | 809 | 13 | $73k | $90k |
| 50481 | Toeterville | Mitchell County | PO Box or unique | – | – | – |
| 50482 | Ventura | Cerro Gordo County | 748 | 25 | $98k | $238k |
| 50483 | Wesley | Kossuth County | 672 | 8 | $89k | $143k |
| 50484 | Woden | Hancock County | 411 | 9 | $66k | $101k |
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates; GeoNames postal codes (CC BY 4.0) for codes without a residential area.