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

Sanders County had the highest median age on 1 July (US county estimates) of 56 counties in 2018, at 54.4 years. Big Horn County had the lowest, at 30.4 years. The median was 45.3 years. Source: the U.S. Census Bureau.

Highest54.4Sanders County

Lowest30.4Big Horn County

Median45.356 counties

Map of counties, 2018

Under 39
39 to 42
42 to 45
45 to 48
48 to 52
52 and over

years, 2018. 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, 2018

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	2018 years	Change on 2017
1	Sanders County	54.4	+0.1
2	Meagher County	53.8	+0.3
3	Lincoln County	53.5	+0.3
4	Mineral County	53.3	+0.3
5	Granite County	52.9	+0.1
6	Madison County	52.7	-0.2
7	Judith Basin County	52.4	+0.3
8	Prairie County	52.3	-0.3
9	Petroleum County	52.1	+1.2
10	Golden Valley County	52	-0.1
11	Musselshell County	51.2	+0.1
12	Carbon County	49.9	+0.2
13	Powder River County	49.6	+0.4
14	Ravalli County	49.5	+0.3
14	Treasure County	49.5	-1.6
16	Jefferson County	48.9	+0.2
17	Stillwater County	48.6	+0.5
18	Deer Lodge County	48.5	+0.1
19	Sweet Grass County	48.3	+0.9
20	Fergus County	47.4	+0.6
21	Park County	46.9	+0.3
22	McCone County	46.7	-1
23	Broadwater County	46.6	-0.3
24	Daniels County	46.5	-0.8
25	Wheatland County	46.3	-0.1
26	Powell County	46.2	-0.2
27	Sheridan County	45.8	+0.8
28	Carter County	45.5	-1.6
29	Teton County	45	+0.1
30	Lake County	44.3	+0.9
31	Valley County	44.2	-0.7
32	Phillips County	44.1	-0.8
33	Wibaux County	43.9	-3.8
34	Beaverhead County	43.7	+0.7
35	Garfield County	43.6	+1
36	Flathead County	42.5	0
37	Liberty County	42.3	-0.5
38	Silver Bow County	41.8	+0.2
39	Dawson County	41.6	+0.8
40	Pondera County	41.3	-0.1
41	Lewis and Clark County	41.2	0
42	Toole County	41	-0.2
43	Custer County	40.6	0
44	Chouteau County	40.1	+0.1
45	Fallon County	38.6	+0.7
45	Yellowstone County	38.6	+0.3
47	Cascade County	38.5	+0.2
48	Richland County	38.4	+0.4
49	Rosebud County	38.1	+0.7
50	Missoula County	37.1	+0.6
51	Hill County	35.1	+0.4
52	Blaine County	34.4	-0.1
53	Gallatin County	33.2	+0.1
54	Glacier County	32.7	+0.2
55	Roosevelt County	32.3	+0.4
56	Big Horn County	30.4	+0.3

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), 2018) [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), 2018. 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=2018. 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), 2018. 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=2018.

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), 2018 [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=2018 (Accessed: 12 October 2026).

BibTeX

@misc{census_counties_in_montana_by_2018,
  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), 2018}},
  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=2018. 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), 2018
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=2018
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-age-july-1-us-counties/montana-counties?period=2018.
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)?

Sanders County, with 54.4 years in 2018, according to the U.S. Census Bureau.

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

Big Horn County, with 30.4 years in 2018.

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.