What are the largest counties in Montana?

Yellowstone County is the largest county in Montana, with 172,692 residents in 2025 (Census PEP). Gallatin County (128,740) and Missoula County (123,513) come next.

Data as of 2025 · updated November 5, 2026

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All 52 ranked Montana counties

Montana counties ranked by population
Rank	County	Residents 2025	Change 2020–25
1	Yellowstone County	172,692	+4.5%
2	Gallatin County	128,740	+7.6%
3	Missoula County	123,513	+4.4%
4	Flathead County	115,429	+10.1%
5	Cascade County	85,029	+0.7%
6	Lewis and Clark County	75,331	+5.8%
7	Ravalli County	48,582	+9.4%
8	Silver Bow County	36,118	+2.6%
9	Lake County	33,392	+6.9%
10	Lincoln County	22,328	+13.1%
11	Park County	18,214	+5.7%
12	Hill County	16,167	−0.5%
13	Sanders County	14,062	+12.9%
14	Glacier County	13,463	−2.0%
15	Jefferson County	13,329	+9.8%
16	Big Horn County	12,752	−2.5%
17	Custer County	12,034	+1.5%
18	Fergus County	11,825	+3.1%
19	Carbon County	11,466	+9.1%
20	Richland County	11,377	−1.3%
21	Roosevelt County	10,242	−5.2%
22	Beaverhead County	10,043	+7.1%
23	Madison County	10,026	+15.8%
24	Deer Lodge County	9,709	+3.0%
25	Stillwater County	9,445	+5.0%
26	Dawson County	8,692	−2.6%
27	Broadwater County	8,493	+23.8%
28	Rosebud County	8,253	−0.7%
29	Valley County	7,385	−2.4%
30	Powell County	7,157	+3.1%
31	Blaine County	6,860	−2.1%
32	Teton County	6,496	+3.9%
33	Pondera County	6,072	+3.2%
34	Chouteau County	5,865	−0.8%
35	Musselshell County	5,582	+17.6%
36	Toole County	5,211	+4.9%
37	Mineral County	5,185	+13.5%
38	Phillips County	4,203	−0.1%
39	Sweet Grass County	3,762	+2.4%
40	Granite County	3,658	+10.6%
41	Sheridan County	3,436	−2.9%
42	Fallon County	2,959	−2.3%
43	Judith Basin County	2,162	+6.8%
44	Meagher County	2,137	+11.2%
45	Wheatland County	2,100	+1.2%
46	Liberty County	1,957	+0.1%
47	Powder River County	1,781	+5.1%
48	McCone County	1,720	−0.6%
49	Daniels County	1,612	−2.3%
50	Carter County	1,383	−1.6%
51	Garfield County	1,148	−1.9%
52	Prairie County	1,112	+1.6%

How this is ranked

The Census Bureau's July 1 resident population estimates for 2025, largest first, with the change since 2020. Counties with fewer than 1,000 residents are not ranked. Areas without an estimate for the same year as the others are not ranked.

Source: U.S. Census Bureau, Population Estimates Program (Vintage 2025). Figures come from public federal statistics and are informational only, not investment advice. Check the source before relying on a number. Methodology: how ranks and figures are built.

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Questions

What is the largest county in Montana?

Yellowstone County is the largest county in Montana, with 172,692 residents in 2025 (Census PEP). Gallatin County (128,740) and Missoula County (123,513) come next.

How is this ranking calculated?

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