Demographics of Jefferson County, Montana

Jefferson County, Montana had 13,329 people on July 1, 2025, by the Census Bureau’s estimate: +1,188 since July 2020. Age, income, poverty, housing and origin below come from the American Community Survey, averaged over 2020–2024, each with its margin of error.

Jefferson County, in four figures

13,329
Population: July 1, 2025, Vintage 2025 estimate.; +9.8%
Change since July 2020: +1,188 people.; 47.1 ±0.5
Median age: ACS 2020–⁠2024.; $95,490 ±$18,478
Median household income: ACS 2020–⁠2024, in 2024 dollars.

Population, year by year

July 1 estimates from the Census Bureau’s Vintage 2025. Each year's change is births less deaths, net moves from abroad and net moves from elsewhere in the country, with the Bureau's small residual. The 2020 row's components run 3 months, from the April census to July 1.

Jefferson County, Montana's population grew 9.8% from July 2020 to July 2025, against +3.1% nationally

The July 1 estimate of Jefferson County, Montana's resident population and the nation's, each year of the Census Bureau's Vintage 2025, as a share of its July 2020 level (= 100).

U.S. Census Bureau — Census Bureau population estimates — counties and Puerto Rico municipios, with components of change

About this chart

The figures

Jefferson County, Montana's population grew 9.8% from July 2020 to July 2025, against +3.1% nationally. The July 1 estimate of Jefferson County, Montana's resident population and the nation's, each year of the Census Bureau's Vintage 2025, as a share of its July 2020 level (= 100).
July 1	Population	Index	United States
2020	12,141	100.0	100.0
2021	12,465	102.7	100.2
2022	12,846	105.8	100.7
2023	13,049	107.5	101.6
2024	13,231	109.0	102.5
2025	13,329	109.8	103.1

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Population of Jefferson County, Montana on July 1 of each year, Vintage 2025
July 1	Population	Change	Births less deaths	From abroad	From elsewhere in the country
2020	12,141	+60	0	0	+61
2021	12,465	+324	−64	0	+411
2022	12,846	+381	−63	+23	+405
2023	13,049	+203	−34	0	+236
2024	13,231	+182	−52	−1	+236
2025	13,329	+98	−54	−2	+156

Age, 2020–2024

The median age is 47.1 ±0.5: for men 47.1 ±0.6 and for women 47.0 ±1.1. Shares are of everyone the survey counts, in the Bureau’s sex-by-age table (B01001).

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People in Jefferson County by age, ACS 2020–2024
Age	People	Share	Montana	United States
Under 5	559 ±31	4.4% ±0.2	5.2% ±<0.1	5.6% ±<0.1
5 to 17	1,996 ±184	15.6% ±1.4	15.8% ±0.2	16.3% ±<0.1
18 to 24	793 ±159	6.2% ±1.2	9.0% ±0.2	9.1% ±<0.1
25 to 44	2,762 ±190	21.6% ±1.5	25.8% ±0.2	26.9% ±<0.1
45 to 64	3,703 ±240	29.0% ±1.9	24.1% ±0.2	24.8% ±<0.1
65 and over	2,961 ±246	23.2% ±1.9	20.1% ±0.2	17.2% ±<0.1

Income and poverty, 2020–2024

Median household income is $95,490 ±$18,478, and income per person $49,303 ±$3,874, in 2024 dollars. The median is $72,509 ±$761 in Montana and $80,734 ±$166 in the United States.

Households by income

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Households in Jefferson County by income, ACS 2020–2024
Household income	Households	Share	Montana	United States
Under $25,000	513 ±126	10.3% ±2.5	15.0% ±0.4	14.6% ±<0.1
$25,000 to $49,999	720 ±166	14.4% ±3.3	19.4% ±0.5	16.7% ±<0.1
$50,000 to $74,999	981 ±191	19.6% ±3.8	17.3% ±0.4	15.5% ±<0.1
$75,000 to $99,999	378 ±97	7.6% ±1.9	13.6% ±0.4	12.6% ±<0.1
$100,000 to $149,999	1,025 ±223	20.5% ±4.4	17.4% ±0.4	17.5% ±<0.1
$150,000 to $199,999	595 ±155	11.9% ±3.1	8.2% ±0.3	9.6% ±<0.1
$200,000 or more	784 ±165	15.7% ±3.3	9.0% ±0.3	13.4% ±0.1

Poverty by age

The poverty rate is the share of people whose family income is below the federal threshold for their family’s size, of everyone for whom the Bureau determines it (B17020).

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Poverty rate in Jefferson County by age, ACS 2020–2024
Age	Below poverty	Rate	Montana	United States
All ages	715 ±193	5.7% ±1.5	11.5% ±0.3	12.5% ±0.1
Under 18	162 ±63	6.6% ±2.5	12.7% ±0.6	16.1% ±0.1
18 to 59	333 ±108	5.3% ±1.7	11.7% ±0.4	11.6% ±0.1
60 and over	220 ±106	5.7% ±2.7	10.3% ±0.4	11.0% ±<0.1

Housing, 2020–2024

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Housing in Jefferson County, ACS 2020–2024
Measure	Jefferson County	Montana	United States
Housing units	5,407 ±27	528,419 ±3,257	143,775,355 ±10,234
Occupied	92.4% ±2.5	86.8% ±0.5	89.9% ±0.1
Vacant	7.6% ±2.5	13.2% ±0.3	10.1% ±0.1
Owner occupied	84.2% ±1.9	69.2% ±0.6	65.2% ±0.3
Renter occupied	15.8% ±2.8	30.8% ±0.4	34.8% ±0.1
Median home value	$446,900 ±$22,371	$375,800 ±$3,433	$332,700 ±$236
Median gross rent	$925 ±$58	$1,081 ±$14	$1,413 ±$2
Median year built	1990 ±3	1981 ±1	1980 ±1

Occupied and vacant are shares of all housing units; owner and renter occupied are shares of occupied units. Value and rent are medians in 2024 dollars.

Origin and place of birth, 2020–2024

Hispanic or Latino origin is not a race in the Census Bureau’s tables. Here the people of Hispanic origin, of any race, are one row, and everyone else is counted by race alone (B03002), so the rows add to the whole.

Hispanic origin and race

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People in Jefferson County by Hispanic origin and race, ACS 2020–2024
Origin	People	Share	Montana	United States
Hispanic or Latino	380 ±0	3.0% ±<0.1	4.6% ±<0.1	19.3% ±<0.1
White alone, not Hispanic	11,569 ±60	90.6% ±0.5	83.6% ±0.2	57.4% ±<0.1
Black alone, not Hispanic	0 to 13	0% to 0.1%	0.4% ±<0.1	11.9% ±<0.1
Asian alone, not Hispanic	50 ±22	0.4% ±0.2	0.8% ±0.1	5.9% ±<0.1
American Indian and Alaska Native alone, not Hispanic	88 to 260	0.7% to 2.0%	5.3% ±0.1	0.5% ±<0.1
Native Hawaiian and Other Pacific Islander alone, not Hispanic	0 to 18	0% to 0.1%	< 0.1% ±<0.1	0.2% ±<0.1
Some other race alone, not Hispanic	0 to 82	0% to 0.6%	0.5% ±0.1	0.6% ±<0.1
Two or more races, not Hispanic	557 ±93	4.4% ±0.7	4.7% ±0.2	4.3% ±<0.1

A range (the estimate less and plus its margin) where the Bureau's estimate is too uncertain to state as one number: a coefficient of variation over 30%.

Place of birth and citizenship

“Born a citizen outside the states” counts people born in Puerto Rico, the island areas, or abroad to American parents. Naturalized citizens and those who are not citizens together make up the people born abroad (B05002).

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People in Jefferson County by place of birth and citizenship, ACS 2020–2024
Born	People	Share	Montana	United States
Born in the state	6,486 ±400	50.8% ±3.1	52.1% ±0.5	57.3% ±<0.1
Born in another state	6,086 ±408	47.6% ±3.2	44.8% ±0.4	26.9% ±<0.1
Born a citizen outside the states	32 to 116	0.3% to 0.9%	0.8% ±0.1	1.7% ±<0.1
Born abroad	128 ±53	1.0% ±0.4	2.3% ±0.1	14.1% ±<0.1
Naturalized citizens	43 to 151	0.3% to 1.2%	1.2% ±0.1	7.4% ±<0.1
Not citizens	6 to 56	< 0.1% to 0.4%	1.1% ±0.1	6.8% ±<0.1

A range (the estimate less and plus its margin) where the Bureau's estimate is too uncertain to state as one number: a coefficient of variation over 30%.

Jefferson County among the counties of Montana

15th of 56 by population, July 2025. Every one is listed on the Montana page.

Counties of Montana near Jefferson County in population, July 2025
County	July 2025	Change since 2020
Lincoln County	22,328	+13.1%
Park County	18,214	+5.7%
Hill County	16,167	−0.5%
Sanders County	14,062	+12.9%
Glacier County	13,463	−2.0%
Jefferson County	13,329	+9.8%
Big Horn County	12,752	−2.5%
Custer County	12,034	+1.5%
Fergus County	11,825	+3.1%
Carbon County	11,466	+9.1%
Richland County	11,377	−1.3%

Elsewhere on the site

Sources

Census Bureau population estimates — counties and Puerto Rico municipios, with components of change — U.S. Census Bureau · U.S. Government work · retrieved September 25, 2026
American Community Survey 5-year estimates — table-based Summary File · U.S. Government work

Data retrieved September 25, 2026