MT · 2026 Census Gazetteer

Montana counties by area

Official, comparable measurements for 56 counties and county equivalents.

Source fields preservedGEOID · ALAND · AWATER

County equivalents56

Combined land145,550.3 mi²

Combined water1,493 mi²

Largest by landBeaverhead County

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.

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.

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.

Complete area table

Sorted from largest to smallest land area.

#	County / equivalent	Land	Water	Water share
1	Beaverhead CountyGEOID 30001	5,542.7 mi²	30.2 mi²	0.5%
2	Phillips CountyGEOID 30071	5,140.4 mi²	71.6 mi²	1.4%
3	Flathead CountyGEOID 30029	5,087.3 mi²	168.7 mi²	3.2%
4	Rosebud CountyGEOID 30087	5,008.1 mi²	17.1 mi²	0.3%
5	Big Horn CountyGEOID 30003	4,997.8 mi²	18.3 mi²	0.4%
6	Valley CountyGEOID 30105	4,926.1 mi²	135.7 mi²	2.7%
7	Garfield CountyGEOID 30033	4,676.6 mi²	172.5 mi²	3.6%
8	Fergus CountyGEOID 30027	4,339.3 mi²	10.7 mi²	0.2%
9	Blaine CountyGEOID 30005	4,227.5 mi²	11.2 mi²	0.3%
10	Chouteau CountyGEOID 30015	3,972.5 mi²	24.2 mi²	0.6%
11	Custer CountyGEOID 30017	3,783.3 mi²	9.9 mi²	0.3%
12	Lincoln CountyGEOID 30053	3,612.6 mi²	62.4 mi²	1.7%
13	Madison CountyGEOID 30057	3,588.2 mi²	15.4 mi²	0.4%
14	Lewis and Clark CountyGEOID 30049	3,458.4 mi²	39.2 mi²	1.1%
15	Carter CountyGEOID 30011	3,340.5 mi²	7.5 mi²	0.2%
16	Powder River CountyGEOID 30075	3,298.2 mi²	0.6 mi²	0%
17	Glacier CountyGEOID 30035	2,995.2 mi²	40.8 mi²	1.3%
18	Hill CountyGEOID 30041	2,899.4 mi²	17.1 mi²	0.6%
19	Park CountyGEOID 30067	2,802.5 mi²	10.8 mi²	0.4%
20	Sanders CountyGEOID 30089	2,760.4 mi²	29.5 mi²	1.1%
21	Cascade CountyGEOID 30013	2,698.2 mi²	13.2 mi²	0.5%
22	McCone CountyGEOID 30055	2,642.2 mi²	39.8 mi²	1.5%
23	Yellowstone CountyGEOID 30111	2,633.4 mi²	15.6 mi²	0.6%
24	Gallatin CountyGEOID 30031	2,605.4 mi²	28.4 mi²	1.1%
25	Missoula CountyGEOID 30063	2,593 mi²	24.9 mi²	1%
26	Meagher CountyGEOID 30059	2,391.9 mi²	2.9 mi²	0.1%
27	Ravalli CountyGEOID 30081	2,391 mi²	9.4 mi²	0.4%
28	Dawson CountyGEOID 30021	2,371.9 mi²	11.5 mi²	0.5%
29	Roosevelt CountyGEOID 30085	2,354.6 mi²	14.9 mi²	0.6%
30	Powell CountyGEOID 30077	2,326 mi²	6.3 mi²	0.3%
31	Teton CountyGEOID 30099	2,271.6 mi²	20.3 mi²	0.9%
32	Richland CountyGEOID 30083	2,084.6 mi²	18.9 mi²	0.9%
33	Carbon CountyGEOID 30009	2,047.9 mi²	13.5 mi²	0.7%
34	Toole CountyGEOID 30101	1,914.9 mi²	30.1 mi²	1.5%
35	Judith Basin CountyGEOID 30045	1,869.7 mi²	0.8 mi²	0%
36	Musselshell CountyGEOID 30065	1,869 mi²	2.7 mi²	0.1%
37	Sweet Grass CountyGEOID 30097	1,855.5 mi²	6.7 mi²	0.4%
38	Stillwater CountyGEOID 30095	1,796.5 mi²	9.2 mi²	0.5%
39	Prairie CountyGEOID 30079	1,736.6 mi²	5.8 mi²	0.3%
40	Granite CountyGEOID 30039	1,727.2 mi²	5.6 mi²	0.3%
41	Sheridan CountyGEOID 30091	1,676.9 mi²	29 mi²	1.7%
42	Jefferson CountyGEOID 30043	1,657 mi²	2.4 mi²	0.1%
43	Petroleum CountyGEOID 30069	1,655.6 mi²	18.9 mi²	1.1%
44	Pondera CountyGEOID 30073	1,624.6 mi²	17 mi²	1%
45	Fallon CountyGEOID 30025	1,620.6 mi²	2.3 mi²	0.1%
46	Lake CountyGEOID 30047	1,490.5 mi²	163.5 mi²	9.9%
47	Liberty CountyGEOID 30051	1,430 mi²	17.1 mi²	1.2%
48	Daniels CountyGEOID 30019	1,426.3 mi²	0.4 mi²	0%
49	Wheatland CountyGEOID 30107	1,422.5 mi²	5 mi²	0.4%
50	Mineral CountyGEOID 30061	1,219.6 mi²	3.8 mi²	0.3%
51	Broadwater CountyGEOID 30007	1,192.4 mi²	45.7 mi²	3.7%
52	Golden Valley CountyGEOID 30037	1,174.4 mi²	1 mi²	0.1%
53	Treasure CountyGEOID 30103	977.8 mi²	6.6 mi²	0.7%
54	Wibaux CountyGEOID 30109	889.6 mi²	0.7 mi²	0.1%
55	Deer Lodge CountyGEOID 30023	736.7 mi²	4.7 mi²	0.6%
56	Silver Bow CountyGEOID 30093	718 mi²	0.6 mi²	0.1%

How to read this table. Land and water areas are Census statistical measurements in square miles. Adding county rows can differ slightly from separately published state totals because of rounding and geographic treatment.