Jefferson County, Montana Facts for Kids

Quick facts for kids Jefferson County
U.S. county
Jefferson County Courthouse in Boulder
Location within the U.S. state of Montana
Montana's location within the U.S.
Country	United States
State	Montana
Founded	February 2, 1865
Named for	Thomas Jefferson
Seat	Boulder
Largest town	Clancy
Area
• Total	1,659 sq mi (4,300 km²)
• Land	1,656 sq mi (4,290 km²)
• Water	2.6 sq mi (7 km²) 0.2%
Population (2020)
• Total	12,085
• Estimate (2022)	12,826
• Density	7/sq mi (3/km²)
Time zone	UTC−7 (Mountain)
• Summer (DST)	UTC−6 (MDT)
Congressional district	2nd
Montana county number 51

Jefferson County is a county in Montana, United States. As of the 2020 census, the population was 12,085. Its county seat is Boulder. The county was created in 1865 and named for President Thomas Jefferson.

Jefferson County is part of the Helena, MT Micropolitan Statistical Area.

Geography
Demographics
- 2020 census
- 2010 census
Communities
See also

Geography

According to the United States Census Bureau, the county has a total area of 1,659 square miles (4,300 km²), of which 1,656 square miles (4,290 km²) is land and 2.6 square miles (6.7 km²) (0.2%) is water.

Major highways

Interstate 15
Interstate 90
U.S. Highway 12
U.S. Highway 287
Montana Highway 2
Montana Highway 41
Montana Highway 55
Montana Highway 69

Adjacent counties

National protected areas

Deerlodge National Forest (part)
Helena National Forest (part)

Demographics

Historical population
Census	Pop.	%±
1870	1,531	—
1880	2,464	60.9%
1890	6,026	144.6%
1900	5,330	−11.5%
1910	5,601	5.1%
1920	5,203	−7.1%
1930	4,133	−20.6%
1940	4,664	12.8%
1950	4,014	−13.9%
1960	4,297	7.1%
1970	5,238	21.9%
1980	7,029	34.2%
1990	7,939	12.9%
2000	10,049	26.6%
2010	11,406	13.5%
2020	12,085	6.0%
2022 (est.)	12,826	12.4%
U.S. Decennial Census 1790–1960, 1900–1990, 1990–2000, 2010–2020

2020 census

As of the 2020 census, there were 12,085 people living in the county.

2010 census

As of the 2010 census, there were 11,406 people, 4,512 households, and 3,301 families residing in the county. The population density was 6.9 inhabitants per square mile (2.7/km²). There were 5,055 housing units at an average density of 3.1 per square mile (1.2/km²). The racial makeup of the county was 95.5% white, 1.4% American Indian, 0.4% Asian, 0.1% black or African American, 0.4% from other races, and 2.2% from two or more races. Those of Hispanic or Latino origin made up 2.0% of the population. In terms of ancestry, 31.3% were German, 19.1% were Irish, 17.2% were English, 10.8% were Norwegian, and 4.2% were American.

Of the 4,512 households, 28.8% had children under the age of 18 living with them, 63.7% were married couples living together, 5.4% had a female householder with no husband present, 26.8% were non-families, and 22.6% of all households were made up of individuals. The average household size was 2.48 and the average family size was 2.90. The median age was 46.2 years.

The median income for a household in the county was $56,695 and the median income for a family was $67,195. Males had a median income of $50,978 versus $34,148 for females. The per capita income for the county was $26,437. About 2.7% of families and 12.8% of the population were below the poverty line, including 5.1% of those under age 18 and 8.6% of those age 65 or over.

Communities

Towns

Boulder (county seat)
Whitehall

Census-designated places

Unincorporated communities

Amazon
Bernice
Corbin
Elk Park
Homestake
Leadville
La Hood Park
Louisville
Pappas Place
Paul Place
Piedmont
Pipestone
Renova

Former communities

Comet
Wickes

Jefferson County, Montana facts for kids

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