Demographics
Historical population| Census | Pop. | Note | %± |
|---|
| 1910 | 7,985 | | — |
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| 1920 | 8,002 | | 0.2% |
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| 1930 | 7,347 | | −8.2% |
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| 1940 | 6,477 | | −11.8% |
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| 1950 | 6,570 | | 1.4% |
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| 1960 | 6,187 | | −5.8% |
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| 1970 | 6,032 | | −2.5% |
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| 1980 | 9,899 | | 64.1% |
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| 1990 | 10,505 | | 6.1% |
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| 2000 | 9,383 | | −10.7% |
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| 2010 | 9,233 | | −1.6% |
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| 2020 | 8,329 | | −9.8% |
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| 2022 (est.) | 8,088 | [7] | −2.9% |
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|
2010 census
As of the 2010 census, there were 9,233 people, 3,395 households, and 2,318 families residing in the county. The population density was 1.8 inhabitants per square mile (0.69/km2). There were 4,057 housing units at an average density of 0.8 per square mile (0.31/km2). The racial makeup of the county was 61.3% white, 34.7% American Indian, 0.5% Asian, 0.3% black or African American, 0.5% from other races, and 2.8% from two or more races. Those of Hispanic or Latino origin made up 3.4% of the population. In terms of ancestry, 25.0% were American, 19.0% were German, 6.9% were English, and 6.6% were Irish.
Of the 3,395 households, 36.4% had children under the age of 18 living with them, 51.3% were married couples living together, 10.6% had a female householder with no husband present, 31.7% were non-families, and 27.6% of all households were made up of individuals. The average household size was 2.70 and the average family size was 3.32. The median age was 36.5 years.
The median income for a household in the county was $44,776 and the median income for a family was $56,282. Males had a median income of $52,500 versus $28,306 for females. The per capita income for the county was $19,844. About 13.6% of families and 18.5% of the population were below the poverty line, including 24.7% of those under age 18 and 21.3% of those age 65 or over.
Yellowstone County is the most populous county in the U.S. state of Montana. As of the 2020 census, the population was 164,731. Its county seat is Billings, the state's most populous city. Like the nearby park, Yellowstone County is named after the Yellowstone River which roughly bisects the county, flowing southwest to northeast. The river, in turn, was named for the yellow sandstone cliffs in what is now Yellowstone County.
Treasure County is a county in the U.S. state of Montana. As of the 2020 census, the population was 762, making it the second-least populous county in Montana. Its county seat is Hysham. The county was split off from Rosebud county in 1919 and named Treasure in hopes of drawing in new settlers.
Sweet Grass County is a county located in the U.S. state of Montana. As of the 2020 census, the population was 3,678. Its county seat is Big Timber. The county was founded in 1895.
Sheridan County is a county in the U.S. state of Montana. As of the 2020 census, the population was 3,539. Its county seat is Plentywood. Its northern boundary is the Canada–United States border south of Saskatchewan.
Roosevelt County is a county in the U.S. state of Montana. As of the 2020 census, the population was 10,794. Its county seat is Wolf Point. Roosevelt County was created by the Montana Legislature in 1919 from a portion of Sheridan County. The name honors former president Theodore Roosevelt, who had died earlier that year.
Powder River County is a county in the U.S. state of Montana. As of the 2020 census, the population was 1,694. Its county seat is Broadus.
Pondera County is a county in the U.S. state of Montana. As of the 2020 census, the population was 5,898. Its county seat is Conrad.
Musselshell County is a county in south-central Montana. As of the 2020 census, the population was 4,730. Its county seat is Roundup.
Garfield County is a county located in the U.S. state of Montana. As of the 2020 census, the population was 1,173. Its county seat is Jordan. Garfield County is noteworthy as the site of the discovery and excavation of four of the world's dozen or so major specimens of Tyrannosaurus rex. A cast of the skull of one of these dinosaurs is on display at the Garfield County Museum.
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. Its county seat and largest town is Miles City. 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. It was originally named Big Horn County of the old Montana Territory, 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.
Big Horn County is a county located in the U.S. state of Montana. As of the 2020 census, the population was 13,124. The county seat is Hardin. The county, like the river and the mountain range, is named after the bighorn sheep in the Rocky Mountains. The county was founded in 1913. It is located on the south line of the state.
Rosebud is a city in Gasconade County, Missouri, United States. The population was 390 at the 2020 census.
Busby is a census-designated place (CDP) in Big Horn County, Montana, United States. It is on the Northern Cheyenne reservation. The population was 745 at the 2010 census.
Ravalli is an unincorporated community in Lake County, Montana, United States. The population was 76 at the 2010 census, down from 119 in 2000. For statistical purposes, the United States Census Bureau has defined Ravalli as a census-designated place (CDP). In the early 1900s, the Pablo-Allard herd in Ravalli was said to be the largest collection of the bison remaining in the U.S. and played a critical role in the conservation of bison.
Melstone is a rural small town in far eastern Musselshell County, Montana, United States, along U.S. Route 12. The population was 126 at the 2020 census. The town was established in 1908 as a base for operating crews on the Chicago, Milwaukee, St. Paul and Pacific Railroad, then under construction in Montana. Although the railroad was abandoned in 1980, Melstone survives as a community center for farmers and ranchers in the lower Musselshell River valley.
Ashland is a census-designated place (CDP) in Rosebud County, Montana, United States. The population was 464 at the 2000 census. Ashland is immediately east of the boundary of the Northern Cheyenne Indian Reservation and also along the Tongue River. It is the location of the St. Labre Indian Catholic High School, established in 1884 as a boarding school by a Catholic mission to the Cheyenne.
Birney is a census-designated place (CDP) in Rosebud County, Montana, United States. The population was 108 at the 2000 census.
Colstrip is a city in Rosebud County, Montana, United States. The population was 2,096 at the 2020 census.
Forsyth is a city in and the county seat of Rosebud County, Montana, United States. The population was 1,647 at the 2020 census. Forsyth was established in 1876 as the first settlement on the Yellowstone River, and in 1882 residents named the town after General James William Forsyth who commanded Fort Maginnis, Montana during the Indian Wars and the 7th Cavalry at the Wounded Knee Massacre. The town has long been a transportation nexus, starting with steamboats on the river and progressing to the Northern Pacific Railway and Interstate 94.
Lame Deer is a census-designated place (CDP) in Rosebud County, Montana, United States. The community is named after Miniconjou Lakota chief Lame Deer, who was killed by the U.S. Army in 1877 under a flag of truce south of the town. It was the site of a trading post from the late 1870s.
United States
Montana 
