Major highways

• U.S. Highway 12
• U.S. Highway 191
• Montana Highway 3

Adjacent counties

National protected area

• Lewis and Clark National Forest (part)

2020 census

As of the 2020 census, there were 2,069 people living in the county.^{[citation needed]}

2010 census

As of the 2010 United States census, there were 2,168 people, 887 households, and 538 families in the county. The population density was 1.5 inhabitants per square mile (0.58/km²). There were 1,197 housing units at an average density of 0.8 per square mile (0.31/km²). The racial makeup of the county was 95.8% white, 0.6% Asian, 0.5% American Indian, 0.3% black or African American, 0.4% from other races, and 2.4% from two or more races. Those of Hispanic or Latino origin made up 1.5% of the population. In terms of ancestry, 35.2% were American, 22.7% were German, 14.1% were English, 11.5% were Irish, and 6.6% were Norwegian.

Of the 887 households, 23.7% had children under the age of 18 living with them, 50.8% were married couples living together, 6.4% had a female householder with no husband present, 39.3% were non-families, and 35.4% of all households were made up of individuals. The average household size was 2.28 and the average family size was 2.99. The median age was 44.9 years.

The median income for a household in the county was $30,321 and the median income for a family was $41,161. Males had a median income of $30,769 versus $17,083 for females. The per capita income for the county was $18,474. About 5.1% of families and 11.5% of the population were below the poverty line, including 8.8% of those under age 18 and 27.6% of those age 65 or over.

Cities

• Harlowton (county seat)
• Judith Gap

Census-designated places

• Duncan Ranch Colony
• Martinsdale Colony
• Shawmut
• Springwater Colony
• Twodot

Other unincorporated communities

• Hedgesville^[10]
• Living Springs^[11]