Counties in Montana by median age on 1 July (US county estimates)

Petroleum County had the highest median age on 1 July (US county estimates) of 56 counties in 2023, at 55.4 years. Big Horn County had the lowest, at 32.3 years. The median was 44.6 years. Source: the U.S. Census Bureau.

Highest55.4Petroleum County

Lowest32.3Big Horn County

Median44.656 counties

Map of counties, 2023

Under 39
39 to 42
42 to 45
45 to 48
48 to 50
50 and over

years, 2023. Source: U.S. Census Bureau, Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2023

years. Source: U.S. Census Bureau, Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2023 years	Change on 2022
1	Petroleum County	55.4	0
2	Sanders County	54.4	-0.2
3	Prairie County	54	+0.7
4	Lincoln County	52.6	0
5	Judith Basin County	51.6	+0.6
5	Mineral County	51.6	-0.2
7	Madison County	51.4	-0.7
8	Meagher County	50.9	0
9	Granite County	50.7	-1.7
10	Deer Lodge County	50.4	+0.3
11	Golden Valley County	50.3	-0.7
12	Carbon County	49.6	+0.4
13	Ravalli County	49.3	0
14	Powder River County	49	-1.3
15	Musselshell County	48.7	0
16	McCone County	48.5	+1
16	Sweet Grass County	48.5	-0.1
18	Stillwater County	48.2	+0.1
19	Wheatland County	47.7	+0.6
20	Jefferson County	47.6	-0.2
21	Wibaux County	47.1	-1.1
22	Daniels County	46.6	-0.3
23	Fergus County	46.2	-0.4
24	Park County	46	-0.4
25	Powell County	45.7	-0.4
25	Sheridan County	45.7	0
27	Carter County	45	+0.1
28	Lake County	44.8	+0.1
29	Broadwater County	44.3	-0.3
30	Valley County	44.2	-0.1
31	Phillips County	43.7	-0.6
32	Beaverhead County	43.6	-0.2
32	Garfield County	43.6	+0.2
34	Chouteau County	43.5	+0.6
35	Treasure County	43.2	-1.6
36	Teton County	43.1	-0.9
37	Flathead County	42.3	0
38	Liberty County	42.2	+0.1
39	Dawson County	41.9	-0.2
40	Lewis and Clark County	41.6	+0.2
40	Silver Bow County	41.6	0
42	Pondera County	41.4	0
43	Custer County	41.3	+0.4
44	Fallon County	40	+0.7
45	Richland County	39.7	+0.2
46	Toole County	39.5	+0.3
47	Yellowstone County	39.2	+0.2
48	Cascade County	39.1	+0.2
49	Missoula County	38.4	+0.3
50	Rosebud County	37.5	-0.2
51	Blaine County	36.5	+1
52	Hill County	35.4	+0.1
53	Gallatin County	34.3	+0.4
53	Glacier County	34.3	+0.5
55	Roosevelt County	32.6	+0.3
56	Big Horn County	32.3	+0.2

Other periods

About this ranking

Age that divides the resident population of a US county into two halves of equal size on 1 July, from Census Bureau population estimates calculated by single year of age.

Counties only: the county file has no state or national medians, and medians cannot be added up. A single-year estimate, unlike median_age, which for US places is a five-year American Community Survey estimate.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. Equal values share a rank.

How to cite

U.S. Census Bureau. Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Census Bureau. (2026). Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage (Counties in Montana by median age on 1 July (US county estimates), 2023) [Data set]. Retrieved October 12, 2026, from https://www.census.gov/programs-surveys/popest/data/data-sets.html

MLA 9

Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage, Counties in Montana by median age on 1 July (US county estimates), 2023. U.S. Census Bureau, 25 June 2026, https://www.census.gov/programs-surveys/popest/data/data-sets.html. Invokely, https://invokely.ai/rankings/median-age-july-1-us-counties/montana-counties?period=2023. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Census Bureau. 2026. Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. Counties in Montana by median age on 1 July (US county estimates), 2023. Dataset. Accessed October 12, 2026. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Also distributed by Invokely, https://invokely.ai/rankings/median-age-july-1-us-counties/montana-counties?period=2023.

Harvard

U.S. Census Bureau (2026) Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage, Counties in Montana by median age on 1 July (US county estimates), 2023 [Dataset]. Available at: https://www.census.gov/programs-surveys/popest/data/data-sets.html, via Invokely: https://invokely.ai/rankings/median-age-july-1-us-counties/montana-counties?period=2023 (Accessed: 12 October 2026).

BibTeX

@misc{census_counties_in_montana_by_2023,
  author = {{U.S. Census Bureau}},
  title = {{Population Estimates Program, county population by age and sex: median age (MEDIAN\_AGE\_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage: Counties in Montana by median age on 1 July (US county estimates), 2023}},
  year = {2026},
  howpublished = {Data set},
  url = {https://www.census.gov/programs-surveys/popest/data/data-sets.html},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/median-age-july-1-us-counties/montana-counties?period=2023. Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: median age (MEDIAN\_AGE\_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.},
}

RIS

TY  - DATA
AU  - U.S. Census Bureau
TI  - Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage: Counties in Montana by median age on 1 July (US county estimates), 2023
PY  - 2026
DA  - 2026/06/25
PB  - U.S. Census Bureau
DB  - Invokely
UR  - https://www.census.gov/programs-surveys/popest/data/data-sets.html
L2  - https://invokely.ai/rankings/median-age-july-1-us-counties/montana-counties?period=2023
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-age-july-1-us-counties/montana-counties?period=2023.
N1  - Publisher attribution: U.S. Census Bureau. Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. https://www.census.gov/programs-surveys/popest/data/data-sets.html. Retrieved 2026-10-12.
ER  -

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Questions

Which county has the highest median age on 1 July (US county estimates)?

Petroleum County, with 55.4 years in 2023, according to the U.S. Census Bureau.

Which county has the lowest median age on 1 July (US county estimates)?

Big Horn County, with 32.3 years in 2023.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Census Bureau, Population Estimates Program, county population by age and sex: median age (MEDIAN_AGE_TOT) on 1 July, 2010 to 2019 from the 2010 to 2020 intercensal file and 2020 onwards from the latest vintage. Retrieved 2026-10-12.