Fastest Growing Counties in Montana (2025)

County
Rank
Change (2020)
2025 Pop.
2020 Pop.
Broadwater County124.69%8,5546,860
Petroleum County224.25%620499
Musselshell County317.6%5,5864,750
Madison County416.14%10,0598,661
Lincoln County514.85%22,66519,734
Sanders County614.66%14,28412,458
Mineral County714.49%5,2304,568
Granite County814.46%3,7913,312
Meagher County912.55%2,1611,920
Carbon County1012.18%11,78510,505
Flathead County1111.81%117,267104,876
Jefferson County1211.04%13,48212,142
Ravalli County1310.02%48,86044,411
Lake County149.76%34,30831,258
Lewis and Clark County158.83%77,46571,177
Beaverhead County168.3%10,1619,382
Gallatin County178.16%129,351119,597
Treasure County186.46%808759
Park County195.69%18,20317,223
Silver Bow County205.61%37,18635,210
Teton County215.53%6,5986,252
Toole County225.49%5,2454,972
Deer Lodge County235.42%9,9319,420
Pondera County245.32%6,1915,878
Judith Basin County255%2,1212,020
Yellowstone County264.58%172,789165,218
Sweet Grass County274.5%3,8353,670
Missoula County284.38%123,525118,347
Powell County294.34%7,2436,942
Fergus County304.33%11,97211,475
Powder River County314.07%1,7651,696
Golden Valley County323.9%853821
Carter County333.13%1,4481,404
Prairie County342.66%1,1201,091
Garfield County352.13%1,1971,172
Stillwater County361.98%9,1819,003
Hill County371.97%16,59216,271
Phillips County381.85%4,2914,213
Liberty County391.02%1,9741,954
Wheatland County400.92%2,0952,076
Custer County410.75%11,95511,866
Cascade County420.34%84,69884,407
Dawson County43-1.21%8,8168,924
Glacier County44-1.59%13,52713,745
Rosebud County45-1.6%8,1768,309
Daniels County46-2.72%1,6091,654
Valley County47-2.89%7,3387,556
Chouteau County48-2.95%5,7255,899
Blaine County49-3.62%6,7537,007
Big Horn County50-3.66%12,60113,080
Richland County51-4.12%11,05911,534
Sheridan County52-4.41%3,3843,540
Fallon County53-4.85%2,8823,029
Wibaux County54-6.31%876935
McCone County55-7.06%1,6061,728
Roosevelt County56-8.5%9,88310,801

Montana County Growth Overview

Montana's counties show varied growth patterns from 2020 to 2025. Broadwater County leads with 24.69% annualized growth, followed by Petroleum County (24.25%) and Musselshell County (17.6%). The largest counties are Yellowstone County (172,789), Gallatin County (129,351), and Missoula County (123,525). Of the 56 counties in Montana, 42 are growing while 14 have experienced population decline. Overall, counties averaged 4.82% annualized growth, with total population growing by 6.02% annually.