Residential delivery area · Iowa
ZIP Code 51003: Alton, IA
ZIP code 51003 uses the postal name Alton, Iowa and lies entirely in Sioux County (Census 2020 ZIP-county file). About 1,900 people live there (Census Bureau, ACS 2020-2024). Median household income is $101,250 (Census Bureau, ACS 2020-2024). By Census place, 4% of its land lies in Alton; 97% is outside any Census place.
- ACS2020-24
- Census2020
- FHFA2025
- ZBP2023
- IRS2022
- Town
- Alton · its only residential ZIP
- County
- Sioux County
- Census places
- Alton
- House district
- IA-4 119th Congress
- State
- Iowa
- Time zone
- Central
- Land area
- 54.4 sq mi · 36 people per sq mi
Where is ZIP code 51003?
51003 centers on 42.990°, -95.986° and covers 54.4 square miles of land plus 0.0 of water. It borders 5 ZIP codes: 51041, 51022, 51238, 51050, 51031.
The map draws ZIP code areas only. For the streets inside 51003, open its center on OpenStreetMap.
Source: U.S. Census Bureau, 2020 ZCTA cartographic boundaries and the 2023 Gazetteer (2020 ZCTAs); ZIP-to-county shares, Census places and House districts (119th Congress) from the Census 2020 relationship files (shares of land); metro area from the OMB delineation (July 2023); town name and time zone from simplemaps US ZIP Codes (CC BY 4.0).
How does 51003 compare with the rest of Sioux County?
| Measure | 51003 | In Sioux County | In IA |
|---|---|---|---|
| People (ACS 2020-2024) | 1,938 | 9th of 19 | 288th of 970 |
| Median household income | $101k | 1st of 12 | 55th of 396 |
| Median home value | $233k | 6th of 14 | 118th of 423 |
Its median household income is higher than in 82% of U.S. residential ZIP codes, and it is denser than 36% of all U.S. residential ZIP codes. ZIP codes at the ACS caps ($250,000 or more for household income, $2,000,000 or more for home value) share the top rank.
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates (B01003, B19013, B25077); ranks by PlainZIP over residential ZIP codes (ZCTAs).
How many people live in 51003?
The 2020 Census counted 1,719 people in 51003; the ACS, which samples households over 2020-2024, estimates 1,938. Between the 2010 and 2020 censuses its population grew 1.1% (its boundary stayed at least 90% the same).
- People, ACS 2020-2024
- 1,938±324 (90% margin)
- 2020 Census count
- 1,719+1.1% since 2010 (1,700)
- Households
- 730
- Median age
- 37.1
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates (B01003, B01002, B11001); 2020 Census (DHC P1); 2010 Census (SF1 P1).
Who lives in 51003?
Of the 1,938 people the ACS estimates in 51003, 26.2% are under 18 and 12.6% are 65 or older. The largest group by race and Hispanic origin is White (not Hispanic) (89.3%).
- Under 1826.2%
- 18 to 6461.2%
- 65 and older12.6%
- White, not Hispanic89.3%
- Hispanic or Latino5.4%
- Other or two or more3.0%
- Black, not Hispanic1.7%
- Asian, not Hispanic0.7%
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates (B01001 age by sex, B03002 Hispanic or Latino origin by race); shares of the estimated population, small ZIP codes carry wide margins.
What do households in 51003 earn?
Median household income is $101,250 (ACS 2020-2024), the highest of the 12 ranked ZIP codes in Sioux County. It is not measurably different from 2015-2019 ($88,780 in 2024 dollars): the change is within the surveys' margins of error.
- Median household income
- $101,250±$13,167
- Income per person
- $44,417
- Below the poverty line
- 2.0%
- Unemployed (of the labor force)
- 2.0%
- Adults 25+ with a bachelor's degree
- 29.2%
- Adjusted gross income per tax return, 2022
- $83,420740 returns; wages 67% of AGI (IRS)
Source: U.S. Census Bureau, ACS 2020-2024 and 2015-2019 5-year estimates (B19013, B19301, B17001, B23025, B15003; 2015-2019 dollars converted with the BLS CPI-U, 1.22699); IRS Statistics of Income, ZIP code data, tax year 2022 (adjusted gross income per return, filed under the address on the return).
What are homes worth in 51003?
FHFA's house price index for 51003, built from repeat sales and appraisals of the same homes, rose 93% from 2015 to 2025 and rose 60% from 2020 to 2025, and moved +15.8% in 2025.
- Median home value (owners' estimate)
- $232,700
- Median gross rent
- $813
- Homes owned by their occupants
- 87.1%
- Housing units
- 788
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates (B25077, B25064, B25003, B25001); FHFA House Price Index, annual five-digit ZIP, updated 2026-03-31.
What businesses are in 51003?
44 business establishments had a location in this ZIP code in 2023, 3 fewer than in 2018; the most are in construction (ZIP Code Business Patterns).
- Construction9
- Transportation and warehousing7
- Other services (except public administration)6
- Retail trade5
- Wholesale trade4
- Manufacturing3
Source: U.S. Census Bureau, ZIP Code Business Patterns 2023 and 2018 (establishments with paid employees, by the business's ZIP code).
Which ZIP codes are next to 51003?
| ZIP | Town | People | Household income | Distance |
|---|---|---|---|---|
| 51041 | Orange City | 7,324 | $84k | 5.2 mi |
| 51022 | Granville | 960 | $97k | 7.1 mi |
| 51238 | Hospers | 1,502 | $74k | 7.5 mi |
| 51050 | Remsen | 2,962 | $93k | 13.2 mi |
| 51031 | Le Mars | 12,808 | $77k | 16.4 mi |
| 51036 | Maurice | 445 | $123k | 10.4 mi (near) |
| 51045 | Oyens | 66 | $114k | 12.3 mi (near) |
| 51250 | Sioux Center | 9,970 | $94k | 13.1 mi (near) |
| 51234 | Boyden | 1,172 | $84k | 14.1 mi (near) |
Source: PlainZIP from the Census 2020 ZCTA boundaries (shared edges) and internal points; figures ACS 2020-2024.