| County | Rank | Change (2020) ↓ | 2025 Pop. | 2020 Pop. |
|---|---|---|---|---|
| Broadwater County | 1 | 24.45% | 8,541 | 6,863 |
| Musselshell County | 2 | 16.38% | 5,527 | 4,749 |
| Madison County | 3 | 15.43% | 9,997 | 8,661 |
| Mineral County | 4 | 15.04% | 5,255 | 4,568 |
| Lincoln County | 5 | 13.96% | 22,501 | 19,744 |
| Sanders County | 6 | 12.86% | 14,064 | 12,461 |
| Jefferson County | 7 | 11.37% | 13,522 | 12,142 |
| Flathead County | 8 | 10.18% | 115,559 | 104,881 |
| Granite County | 9 | 10.07% | 3,639 | 3,306 |
| Carbon County | 10 | 10.04% | 11,570 | 10,514 |
| Ravalli County | 11 | 9.45% | 48,614 | 44,417 |
| Beaverhead County | 12 | 7.96% | 10,123 | 9,377 |
| Meagher County | 13 | 7.74% | 2,073 | 1,924 |
| Lake County | 14 | 7.37% | 33,551 | 31,247 |
| Stillwater County | 15 | 7.34% | 9,663 | 9,002 |
| Gallatin County | 16 | 7.05% | 128,039 | 119,607 |
| Lewis and Clark County | 17 | 5.99% | 75,446 | 71,179 |
| Park County | 18 | 5.69% | 18,210 | 17,229 |
| Deer Lodge County | 19 | 5.45% | 9,937 | 9,423 |
| Judith Basin County | 20 | 4.94% | 2,123 | 2,023 |
| Golden Valley County | 21 | 4.63% | 859 | 821 |
| Yellowstone County | 22 | 4.38% | 172,439 | 165,210 |
| Missoula County | 23 | 4.28% | 123,420 | 118,353 |
| Toole County | 24 | 4.25% | 5,178 | 4,967 |
| Fergus County | 25 | 3.82% | 11,908 | 11,470 |
| Teton County | 26 | 3.13% | 6,449 | 6,253 |
| Pondera County | 27 | 2.91% | 6,048 | 5,877 |
| Powder River County | 28 | 2.6% | 1,737 | 1,693 |
| Powell County | 29 | 2.59% | 7,118 | 6,938 |
| Sweet Grass County | 30 | 2.59% | 3,765 | 3,670 |
| Silver Bow County | 31 | 2.46% | 36,075 | 35,210 |
| Prairie County | 32 | 1.74% | 1,109 | 1,090 |
| McCone County | 33 | 1.21% | 1,750 | 1,729 |
| Petroleum County | 34 | 1% | 507 | 502 |
| Custer County | 35 | 0.44% | 11,915 | 11,863 |
| Cascade County | 36 | 0.01% | 84,421 | 84,411 |
| Rosebud County | 37 | -0.49% | 8,265 | 8,306 |
| Chouteau County | 38 | -0.57% | 5,883 | 5,917 |
| Carter County | 39 | -0.64% | 1,398 | 1,407 |
| Phillips County | 40 | -0.74% | 4,180 | 4,211 |
| Blaine County | 41 | -1.16% | 6,922 | 7,003 |
| Wheatland County | 42 | -1.16% | 2,048 | 2,072 |
| Daniels County | 43 | -1.75% | 1,624 | 1,653 |
| Hill County | 44 | -1.87% | 15,949 | 16,253 |
| Wibaux County | 45 | -1.92% | 918 | 936 |
| Garfield County | 46 | -2.13% | 1,146 | 1,171 |
| Valley County | 47 | -2.22% | 7,393 | 7,561 |
| Glacier County | 48 | -2.29% | 13,429 | 13,744 |
| Big Horn County | 49 | -2.42% | 12,767 | 13,083 |
| Liberty County | 50 | -2.5% | 1,909 | 1,958 |
| Dawson County | 51 | -3.14% | 8,642 | 8,922 |
| Sheridan County | 52 | -3.68% | 3,406 | 3,536 |
| Fallon County | 53 | -4.49% | 2,893 | 3,029 |
| Richland County | 54 | -4.96% | 10,962 | 11,534 |
| Treasure County | 55 | -6.2% | 711 | 758 |
| Roosevelt County | 56 | -6.8% | 10,067 | 10,802 |
Montana's counties show varied growth patterns from 2020 to 2025. Broadwater County leads with 24.45% annualized growth, followed by Musselshell County (16.38%) and Madison County (15.43%). The largest counties are Yellowstone County (172,439), Gallatin County (128,039), and Missoula County (123,420). Of the 56 counties in Montana, 36 are growing while 20 have experienced population decline. Overall, counties averaged 3.57% annualized growth, with total population growing by 5.14% annually.
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