| County: | Custer County |
| State: | Montana |
| Founded Date: | June 2 |
| Founded Year: | 1865 |
| Seat Wl: | Miles City |
| Largest City Wl: | Miles City |
| Area Total Sq Mi: | 3793 |
| Area Land Sq Mi: | 3783 |
| Area Water Sq Mi: | 9.9 |
| Area Percentage: | 0.3 |
| Population As Of: | 2020 |
| Population Total: | 11867 |
| Pop Est As Of: | 2022 |
| Population Est: | 12032 |
| Population Density Sq Mi: | auto |
| Time Zone: | Mountain |
| Ex Image: | Miles City MT Custer County Courthouse.jpg |
| Ex Image Cap: | Custer County Courthouse of Art Deco style architecture of the 1930s era, in the county seat and largest town of Miles City |
| Website: | https://custercountymt.com/ |
| District: | 2nd |
| Named For: | George Armstrong Custer (1839-1876) |
| Footnotes: |
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Custer County is a county located in the southeast part of the U.S. state of Montana. As of the 2020 U.S. census, the population was 11,867.[1] Its county seat and largest town is Miles City.[2] The county was established after the end of the American Civil War (1861-1865), on June 2, 1865, as one of the nine original counties of the new western federal Territory of Montana, which had been formed the previous May of 1864 by the United States Congress, with the approval of 16th President Abraham Lincoln (1809-1865, served 1861-1865). It was originally named Big Horn County of the old Montana Territory,[3] and was renamed on February 16, 1877, in honor of Lieutenant Colonel George Armstrong Custer (1839-1876), commander of the famous 7th Cavalry Regiment of the United States Army, recently massacred and killed in the nearby Battle of the Little Bighorn, in the later portion of the American Indian Wars, the year before in June 1876.[4]
According to the United States Census Bureau, the county has a total area of, of which is land and (0.3%) is water.[5]
According to the Köppen Climate Classification system, Custer County has a mostly cold semi-arid climate, abbreviated "BSk" on climate maps.
As of the 2020 census, there were 11,867 people living in the county.
As of the 2010 census, there were 11,699 people, 5,031 households, and 3,014 families living in the county. The population density was . There were 5,560 housing units at an average density of . The racial makeup of the county was 95.5% white, 1.7% American Indian, 0.3% black or African American, 0.3% Asian, 0.1% Pacific islander, 0.5% from other races, and 1.6% from two or more races. Those of Hispanic or Latino origin made up 2.2% of the population. In terms of ancestry, 33.6% were German, 18.3% were Irish, 14.3% were American, 14.1% were Norwegian, and 10.6% were English.
Of the 5,031 households, 27.3% had children under the age of 18 living with them, 46.6% were married couples living together, 9.0% had a female householder with no husband present, 40.1% were non-families, and 34.3% of all households were made up of individuals. The average household size was 2.24 and the average family size was 2.88. The median age was 42.1 years.
The median income for a household in the county was $38,913 and the median income for a family was $49,011. Males had a median income of $37,535 versus $26,576 for females. The per capita income for the county was $21,676. About 12.4% of families and 15.7% of the population were below the poverty line, including 19.8% of those under age 18 and 14.6% of those age 65 or over.
Agriculture (dryland farming) and cattle raising provide the bulk of Custer County economy.[6] Miles City serves as the center of commerce in an area extending for 100 miles in every direction.[7] As of 2009 the county's largest employers were Holy Rosary Healthcare, Sanjel USA, Stockman Bank, and Walmart.[7]