ZIP Codes of Grant County, SD

Population & People
Population & People
Total Population
377
Household Income
Household Income
Median Income
$75,417
Housing
Housing
Total Housing Units
209
Business & Economy
Business & Economy
Total Businesses
276
Employment
Employment
Employment Rate
45.16%
Education
Education
Bachelor's Degree+
13.90%
Source: U.S. Census ACS 2024 5-Year Estimates · rolled up across the 1 ZIPs in this county.
Data Last Updated: June 1, 2026
ZIP Codes:8 ZIP Codes (8 Standard, 0 PO Box, 0 Unique) [See All]
Area Code:605
Timezone:Central (GMT -06:00)
Local Time:2:13:42 PM
Population:377 [See All]
FIPS:46051
Land Area:647 sq mi
Water Area:12 sq mi
Coordinates:44.9867, -96.4065
Quick Link:
https://www.zip-codes.com/county/sd-grant.asp
Need Grant data in your app? Look up ZIP, county, and city data with a single API call.
Try Free
Notable population decline
Lost 24.1% of residents since 2014.
Extreme education divide
Bachelor's share ranges 1.1% to 54.7% across ZIPs — a 54-point gap.
Among South Dakota's 5 oldest counties
Median age 54.2.

Standout ZIPs in this County


Most Populous
Milbank · 4,883 people
61.9% of county total
Highest Income
Twin Brooks · $98,333 median
1.2× county average
Largest Land Area
Milbank · 164.7 sq mi
Spans the most ground
Fastest Growth
Big Stone City · 40.2% (10-yr)
1,130 → 1,584 residents
Most Educated
Milbank · 28.6% bachelor's+
998 of 3,486 adults 25+

Things worth knowing about Grant County


7,883 residents live across 8 ZIPs covering 647 sq mi, served by 8 distinct USPS-recognized cities.

Population moved from 7,475 to 7,883 from 2014 to 2024 — a +5.5% change. 4 ZIPs gained residents, 4 lost.

The county's wealthiest ZIP 57269 (Twin Brooks, $98,333 median) and poorest ZIP 57265 (Strandburg, $69,519) are 17.1 miles apart — a 1.4× income gap across local geography.

Median home values vary 5.5× across this county — from $75,000 in 57251 (Marvin) to $410,600 in 57269 (Twin Brooks).

Density varies 14× across the county — from 2 people/sq mi in 57269 (Twin Brooks) to 30 in 57252 (Milbank).

Educational attainment ranges from 1.1% bachelor's+ in 57265 (Strandburg) to 54.7% in 57269 (Twin Brooks) — the breadth of educational profiles across the area.

Within South Dakota, this is the #93 most populous of 93 counties and ranks #48 for median household income .

Weighted by population, the typical household earns about $75,578 across the county — reflecting what a typical resident sees, not a simple ZIP average.

25.8% of adults age 25+ hold a bachelor's degree or higher (1,447 of 5,600 reporting).

8 Standard delivery, 0 PO Box only, 0 single-entity Unique ZIPs serve this county.

Stories about Grant County


Big & sparse

A frontier county — vast land area with only a few residents per square mile. Daily life looks very different here than in the country's denser counties.

Total area
647
square miles
Avg density
12.2
people per sq mi
Population
7,883
across 8 ZIPs
Milbank
164.7 sq mi
4,883 residents
Revillo
121.3 sq mi
477 residents
Twin Brooks
89.4 sq mi
186 residents

Single-ZIP anchor

One ZIP holds the majority of this county's population — a sign of a county built around a single city or town.

Milbank

Population decline

Grant County lost 24.1% of residents between 2014 and 2024. ZIPs that shed the largest share:

Twin Brooks
-66.7%
559 → 186 residents

All ZIP Codes in Grant County


ZIPCityTypePopulationMedian IncomeArea (sq mi)10-yr Growth
57252MilbankStandard4,883$70,479164.77.9%
57216Big Stone CityStandard1,584$88,20359.540.2%
57259RevilloStandard477$80,250121.32.1%
57251MarvinStandard228$72,29243.110.7%
57265StrandburgStandard202$69,51979.8-15.5%
57264StockholmStandard191$79,58350.4-1.5%
57269Twin BrooksStandard186$98,33389.4-66.7%
57246LaboltStandard132$72,91739.1-14.3%

Adjacent & Nearby Counties