ZIP Code 51003

51003 is one of Iowa's ZIP codes, delivering to addresses in Alton, Sioux County.

City: Alton
County: Sioux County
State: Iowa
Prefix: 510xx

Where this code sits

51003 is part of the 510xx range, the group of codes handled by one mail processing centre. It is the only ZIP code delivering to Alton.

Alton Iowa ZIP codes →

Area codes over the same ground

Postal and telephone geography are drawn separately, so these codes cover the area 51003 delivers to without sharing its boundary.

712 Area code 712

ZIP codes nearest 51003

The ZIP codes whose reference points sit closest to 51003.
ZIP code	Distance	Delivers to
ZIP code 51041	3.4 mi	Orange City, IA
ZIP code 51022	6.1 mi	Granville, IA
ZIP code 51036	7.6 mi	Maurice, IA
ZIP code 51238	8.7 mi	Hospers, IA
ZIP code 51250	11 mi	Sioux Center, IA
ZIP code 51045	11 mi	Oyens, IA
ZIP code 51050	12 mi	Remsen, IA
ZIP code 51031	15 mi	Le Mars, IA

Straight-line distance between place reference points, not driving distance. Where a place has no Census Gazetteer point, its postal centroid is used instead.

Each point is the reference point for 51003, plotted from its record coordinates.

Reference points and footprint
Not an official NANPA boundary
Not a USPS delivery area

Scope ZIP code 51003. Source GeoNames US postal codes (2026-07 postal dump) and Census 2024 county Gazetteer (2024 Gazetteer). Updated 15 July 2026. A ZIP code is a set of delivery routes, not an area; the point shown is a record coordinate, not a centre.