County Maps US

Custer County, Montana

A county in Montana, ranked 17 of 56 by population.

CountyFIPS 30017

Within Montana
Custer County, highlighted, with the areas around it. Boundaries generalised from the 2025 Census cartographic boundary file; neighbour fills carry no data.

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Population
12,034
+174 (+1.5%) since 2020
Land area
3,783
square miles. A further 0.3% of the total area is water
Population density
3.2
people per square mile, computed rather than published
County seat
Miles City
Seat of county government.
Established
1865
160 years ago
Largest city
Miles City city
Population 8,450.

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; Wikidata (CC0), Wikidata. Retrieved 30 August 2026.

Satellite view

Aerial imagery of Custer County with its boundary drawn on top. A map shows you the shape; this shows you what is inside it, and which side of the line a place falls on.

Aerial view of Custer County, Montana from the USGS National Map, with its boundary outlined
Imagery: USGS National Map, USGS Imagery Only, public domain, requested from USGS by your browser when you reach this point on the page, at 756 by 800 pixels. The boundary is the 2025 Census cartographic boundary file, reprojected to Web Mercator to match the imagery. You can also open the USGS National Map viewer.

Where Custer County ranks

Position among the 56 counties of Montana, and among all 3,144 US counties and county-equivalents. Computed from the figures on this page.

MeasureValueIn MontanaNationally
Population12,03417th of 562,278th of 3,144
Land area3,783 sq mi11th of 56132nd of 3,144
Population density3.2 per sq mi25th of 562,887th of 3,144
Median household income$70,60517th of 561,157th of 3,143

Full data for Custer County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population12,034Vintage 2025 Population Estimates
Population in 202011,860Vintage 2025 Population Estimates
2020 estimates base?11,862Vintage 2025 Population Estimates
Land area3,783 sq mi2025 Gazetteer Files
Water area9.9 sq mi2025 Gazetteer Files
Total area3,793 sq mi2025 Gazetteer Files
Population density?3.2 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$70,605American Community Survey 2020-2024 5-Year Estimates
Median home value$219,100American Community Survey 2020-2024 5-Year Estimates
Median age42.7American Community Survey 2020-2024 5-Year Estimates
Households5,038American Community Survey 2020-2024 5-Year Estimates
Housing units5,784American Community Survey 2020-2024 5-Year Estimates

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026. Population density is computed here, not published: it divides the Vintage 2025 population estimate by the 2025 Gazetteer land area, which are two different Census products. Retrieved 30 August 2026.

How the population changed

The Census Bureau publishes the components behind an estimate, not just the total. For the year to July 2025:

Births minus deaths
+4
138 births, 134 deaths
Net migration
+53
More people moved in than moved out.

Source: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026. Retrieved 30 August 2026.

The 6 areas bordering Custer County

Ordered by the length of the border actually shared, which the Census Bureau publishes in its county adjacency file and which no other county reference presents.

Bordering areaStateShared borderPopulation
Prairie CountyMontana91 mi1,112
Rosebud CountyMontana78 mi8,253
Powder River CountyMontana58 mi1,781
Fallon CountyMontana42 mi2,959
Carter CountyMontana29 mi1,383
Garfield CountyMontana1.0 mi1,148

Source: US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. Retrieved 30 August 2026.

All 56 counties of Montana

Open the interactive Montana county map, or jump straight to any of them.

Data on this page last rebuilt 30 August 2026. How these figures are produced.