Montana County Area & Size Rankings

Understanding Montana’s county areas

The land-area range runs from Silver Bow County at 718 mi² to Beaverhead County at 5,542.7 mi². The largest has 7.7 times the land area of the smallest and accounts for 3.8% of the combined county land in Montana. Compare with every state’s largest county.

The median county-equivalent land area is 2,363.3 mi², above the national median of 604.5 mi². The median describes the middle of the county size distribution; it does not describe how people or development are distributed. A state with a few very large counties can have a much smaller median than its largest entry suggests.

Where water changes the picture

Garfield County has the most assigned water area, at 172.5 mi². Lake County has the highest water share, with water making up 9.9% of its total area. Water area and water percentage answer different questions: the first measures an amount, while the second measures the mix of land and water.

Across all 56 entries, water accounts for 1% of the combined total area. This is calculated from the summed land and water measurements, rather than averaging county percentages, which would give each small and large county equal weight.

Where people live

An estimated 1,144,694 people lived in Montana on July 1, 2025 (+5.6% since 2020), or 0.3% of the national total in this dataset. Yellowstone County is the most populous county equivalent, with 172,692 residents — 15.1% of the state. The largest by land, Beaverhead County, has 10,043.

Across the state there are 7.9 people per square mile of land. County densities range from 66 in Yellowstone County to 0.25 in Garfield County; the median county equivalent has 2.8. Switch the map above to density to see where the state’s population concentrates.

Compare the largest and smallest county equivalents in Montana to see land, water, and total area on the same scale.

These calculations use the 2026 Census county records listed below. County-equivalent boundaries vary between states; area alone does not measure population, density, or usable land. See coverage and calculation rules.

#	County / equivalent	Land	Water	Water share	Population	Per mi²
1	Beaverhead CountyGEOID 30001	5,542.7 mi²	30.2 mi²	0.5%	10,043	1.8
2	Phillips CountyGEOID 30071	5,140.4 mi²	71.6 mi²	1.4%	4,203	0.82
3	Flathead CountyGEOID 30029	5,087.3 mi²	168.7 mi²	3.2%	115,429	23
4	Rosebud CountyGEOID 30087	5,008.1 mi²	17.1 mi²	0.3%	8,253	1.6
5	Big Horn CountyGEOID 30003	4,997.8 mi²	18.3 mi²	0.4%	12,752	2.6
6	Valley CountyGEOID 30105	4,926.1 mi²	135.7 mi²	2.7%	7,385	1.5
7	Garfield CountyGEOID 30033	4,676.6 mi²	172.5 mi²	3.6%	1,148	0.25
8	Fergus CountyGEOID 30027	4,339.3 mi²	10.7 mi²	0.2%	11,825	2.7
9	Blaine CountyGEOID 30005	4,227.5 mi²	11.2 mi²	0.3%	6,860	1.6
10	Chouteau CountyGEOID 30015	3,972.5 mi²	24.2 mi²	0.6%	5,865	1.5
11	Custer CountyGEOID 30017	3,783.3 mi²	9.9 mi²	0.3%	12,034	3.2
12	Lincoln CountyGEOID 30053	3,612.6 mi²	62.4 mi²	1.7%	22,328	6.2
13	Madison CountyGEOID 30057	3,588.2 mi²	15.4 mi²	0.4%	10,026	2.8
14	Lewis and Clark CountyGEOID 30049	3,458.4 mi²	39.2 mi²	1.1%	75,331	22
15	Carter CountyGEOID 30011	3,340.5 mi²	7.5 mi²	0.2%	1,383	0.41
16	Powder River CountyGEOID 30075	3,298.2 mi²	0.6 mi²	0%	1,781	0.54
17	Glacier CountyGEOID 30035	2,995.2 mi²	40.8 mi²	1.3%	13,463	4.5
18	Hill CountyGEOID 30041	2,899.4 mi²	17.1 mi²	0.6%	16,167	5.6
19	Park CountyGEOID 30067	2,802.5 mi²	10.8 mi²	0.4%	18,214	6.5
20	Sanders CountyGEOID 30089	2,760.4 mi²	29.5 mi²	1.1%	14,062	5.1
21	Cascade CountyGEOID 30013	2,698.2 mi²	13.2 mi²	0.5%	85,029	32
22	McCone CountyGEOID 30055	2,642.2 mi²	39.8 mi²	1.5%	1,720	0.65
23	Yellowstone CountyGEOID 30111	2,633.4 mi²	15.6 mi²	0.6%	172,692	66
24	Gallatin CountyGEOID 30031	2,605.4 mi²	28.4 mi²	1.1%	128,740	49
25	Missoula CountyGEOID 30063	2,593 mi²	24.9 mi²	1%	123,513	48
26	Meagher CountyGEOID 30059	2,391.9 mi²	2.9 mi²	0.1%	2,137	0.89
27	Ravalli CountyGEOID 30081	2,391 mi²	9.4 mi²	0.4%	48,582	20
28	Dawson CountyGEOID 30021	2,371.9 mi²	11.5 mi²	0.5%	8,692	3.7
29	Roosevelt CountyGEOID 30085	2,354.6 mi²	14.9 mi²	0.6%	10,242	4.3
30	Powell CountyGEOID 30077	2,326 mi²	6.3 mi²	0.3%	7,157	3.1
31	Teton CountyGEOID 30099	2,271.6 mi²	20.3 mi²	0.9%	6,496	2.9
32	Richland CountyGEOID 30083	2,084.6 mi²	18.9 mi²	0.9%	11,377	5.5
33	Carbon CountyGEOID 30009	2,047.9 mi²	13.5 mi²	0.7%	11,466	5.6
34	Toole CountyGEOID 30101	1,914.9 mi²	30.1 mi²	1.5%	5,211	2.7
35	Judith Basin CountyGEOID 30045	1,869.7 mi²	0.8 mi²	0%	2,162	1.2
36	Musselshell CountyGEOID 30065	1,869 mi²	2.7 mi²	0.1%	5,582	3
37	Sweet Grass CountyGEOID 30097	1,855.5 mi²	6.7 mi²	0.4%	3,762	2
38	Stillwater CountyGEOID 30095	1,796.5 mi²	9.2 mi²	0.5%	9,445	5.3
39	Prairie CountyGEOID 30079	1,736.6 mi²	5.8 mi²	0.3%	1,112	0.64
40	Granite CountyGEOID 30039	1,727.2 mi²	5.6 mi²	0.3%	3,658	2.1
41	Sheridan CountyGEOID 30091	1,676.9 mi²	29 mi²	1.7%	3,436	2
42	Jefferson CountyGEOID 30043	1,657 mi²	2.4 mi²	0.1%	13,329	8
43	Petroleum CountyGEOID 30069	1,655.6 mi²	18.9 mi²	1.1%	548	0.33
44	Pondera CountyGEOID 30073	1,624.6 mi²	17 mi²	1%	6,072	3.7
45	Fallon CountyGEOID 30025	1,620.6 mi²	2.3 mi²	0.1%	2,959	1.8
46	Lake CountyGEOID 30047	1,490.5 mi²	163.5 mi²	9.9%	33,392	22
47	Liberty CountyGEOID 30051	1,430 mi²	17.1 mi²	1.2%	1,957	1.4
48	Daniels CountyGEOID 30019	1,426.3 mi²	0.4 mi²	0%	1,612	1.1
49	Wheatland CountyGEOID 30107	1,422.5 mi²	5 mi²	0.4%	2,100	1.5
50	Mineral CountyGEOID 30061	1,219.6 mi²	3.8 mi²	0.3%	5,185	4.3
51	Broadwater CountyGEOID 30007	1,192.4 mi²	45.7 mi²	3.7%	8,493	7.1
52	Golden Valley CountyGEOID 30037	1,174.4 mi²	1 mi²	0.1%	844	0.72
53	Treasure CountyGEOID 30103	977.8 mi²	6.6 mi²	0.7%	728	0.74
54	Wibaux CountyGEOID 30109	889.6 mi²	0.7 mi²	0.1%	885	0.99
55	Deer Lodge CountyGEOID 30023	736.7 mi²	4.7 mi²	0.6%	9,709	13
56	Silver Bow CountyGEOID 30093	718 mi²	0.6 mi²	0.1%	36,118	50

County / equivalent

Land

Water

Water share

Population

Per mi²

Beaverhead CountyGEOID 30001

5,542.7 mi²

30.2 mi²

0.5%

10,043

1.8

Phillips CountyGEOID 30071

5,140.4 mi²

71.6 mi²

1.4%

4,203

0.82

Flathead CountyGEOID 30029

5,087.3 mi²

168.7 mi²

3.2%

115,429

Rosebud CountyGEOID 30087

5,008.1 mi²

17.1 mi²

0.3%

8,253

1.6

Big Horn CountyGEOID 30003

4,997.8 mi²

18.3 mi²

0.4%

12,752

2.6

Valley CountyGEOID 30105

4,926.1 mi²

135.7 mi²

2.7%

7,385

1.5

Garfield CountyGEOID 30033

4,676.6 mi²

172.5 mi²

3.6%

1,148

0.25

Fergus CountyGEOID 30027

4,339.3 mi²

10.7 mi²

0.2%

11,825

2.7

Blaine CountyGEOID 30005

4,227.5 mi²

11.2 mi²

0.3%

6,860

1.6

Chouteau CountyGEOID 30015

3,972.5 mi²

24.2 mi²

0.6%

5,865

1.5

Custer CountyGEOID 30017

3,783.3 mi²

9.9 mi²

0.3%

12,034

3.2

Lincoln CountyGEOID 30053

3,612.6 mi²

62.4 mi²

1.7%

22,328

6.2

Madison CountyGEOID 30057

3,588.2 mi²

15.4 mi²

0.4%

10,026

2.8

Lewis and Clark CountyGEOID 30049

3,458.4 mi²

39.2 mi²

1.1%

75,331

Carter CountyGEOID 30011

3,340.5 mi²

7.5 mi²

0.2%

1,383

0.41

Powder River CountyGEOID 30075

3,298.2 mi²

0.6 mi²

1,781

0.54

Glacier CountyGEOID 30035

2,995.2 mi²

40.8 mi²

1.3%

13,463

4.5

Hill CountyGEOID 30041

2,899.4 mi²

17.1 mi²

0.6%

16,167

5.6

Park CountyGEOID 30067

2,802.5 mi²

10.8 mi²

0.4%

18,214

6.5

Sanders CountyGEOID 30089

2,760.4 mi²

29.5 mi²

1.1%

14,062

5.1

Cascade CountyGEOID 30013

2,698.2 mi²

13.2 mi²

0.5%

85,029

McCone CountyGEOID 30055

2,642.2 mi²

39.8 mi²

1.5%

1,720

0.65

Yellowstone CountyGEOID 30111

2,633.4 mi²

15.6 mi²

0.6%

172,692

Gallatin CountyGEOID 30031

2,605.4 mi²

28.4 mi²

1.1%

128,740

Missoula CountyGEOID 30063

2,593 mi²

24.9 mi²

123,513

Meagher CountyGEOID 30059

2,391.9 mi²

2.9 mi²

0.1%

2,137

0.89

Ravalli CountyGEOID 30081

2,391 mi²

9.4 mi²

0.4%

48,582

Dawson CountyGEOID 30021

2,371.9 mi²

11.5 mi²

0.5%

8,692

3.7

Roosevelt CountyGEOID 30085

2,354.6 mi²

14.9 mi²

0.6%

10,242

4.3

Powell CountyGEOID 30077

2,326 mi²

6.3 mi²

0.3%

7,157

3.1

Teton CountyGEOID 30099

2,271.6 mi²

20.3 mi²

0.9%

6,496

2.9

Richland CountyGEOID 30083

2,084.6 mi²

18.9 mi²

0.9%

11,377

5.5

Carbon CountyGEOID 30009

2,047.9 mi²

13.5 mi²

0.7%

11,466

5.6

Toole CountyGEOID 30101

1,914.9 mi²

30.1 mi²

1.5%

5,211

2.7

Judith Basin CountyGEOID 30045

1,869.7 mi²

0.8 mi²

2,162

1.2

Musselshell CountyGEOID 30065

1,869 mi²

2.7 mi²

0.1%

5,582

Sweet Grass CountyGEOID 30097

1,855.5 mi²

6.7 mi²

0.4%

3,762

Stillwater CountyGEOID 30095

1,796.5 mi²

9.2 mi²

0.5%

9,445

5.3

Prairie CountyGEOID 30079

1,736.6 mi²

5.8 mi²

0.3%

1,112

0.64

Granite CountyGEOID 30039

1,727.2 mi²

5.6 mi²

0.3%

3,658

2.1

Sheridan CountyGEOID 30091

1,676.9 mi²

29 mi²

1.7%

3,436

Jefferson CountyGEOID 30043

1,657 mi²

2.4 mi²

0.1%

13,329

Petroleum CountyGEOID 30069

1,655.6 mi²

18.9 mi²

1.1%

548

0.33

Pondera CountyGEOID 30073

1,624.6 mi²

17 mi²

6,072

3.7

Fallon CountyGEOID 30025

1,620.6 mi²

2.3 mi²

0.1%

2,959

1.8

Lake CountyGEOID 30047

1,490.5 mi²

163.5 mi²

9.9%

33,392

Liberty CountyGEOID 30051

1,430 mi²

17.1 mi²

1.2%

1,957

1.4

Daniels CountyGEOID 30019

1,426.3 mi²

0.4 mi²

1,612

1.1

Wheatland CountyGEOID 30107

1,422.5 mi²

5 mi²

0.4%

2,100

1.5

Mineral CountyGEOID 30061

1,219.6 mi²

3.8 mi²

0.3%

5,185

4.3

Broadwater CountyGEOID 30007

1,192.4 mi²

45.7 mi²

3.7%

8,493

7.1

Golden Valley CountyGEOID 30037

1,174.4 mi²

1 mi²

0.1%

844

0.72

Treasure CountyGEOID 30103

977.8 mi²

6.6 mi²

0.7%

728

0.74

Wibaux CountyGEOID 30109

889.6 mi²

0.7 mi²

0.1%

885

0.99

Deer Lodge CountyGEOID 30023

736.7 mi²

4.7 mi²

0.6%

9,709

Silver Bow CountyGEOID 30093

718 mi²

0.6 mi²

0.1%

36,118

Montana counties by area

Understanding Montana’s county areas

Where water changes the picture

Where people live

Complete area table