RANKING · 2020 CENSUS · 56 SHOWN OF 56

Largest by population, Montana counties · 2020

The most populous Montana counties as of the 2020 population estimates. This list covers the 56 counties in Montana that qualify, ranked against each other statewide.

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SAME RANKING BYCities States Metros ZIP codes

RELATEDFastest growing Fastest shrinking Most population gained Most population lost Most densely populated Most sparsely populated

YEAR1990 2000 2010 2020 2025

RANKPLACESTATETOTAL POPULATIONVS 2000

01Yellowstone County, MTMT164,731+27%

02Gallatin County, MTMT118,960+75%

03Missoula County, MTMT117,922+23%

04Flathead County, MTMT104,357+40%

05Cascade County, MTMT84,414+5%

06Lewis and Clark County, MTMT70,973+27%

07Ravalli County, MTMT44,174+22%

08Silver Bow County, MTMT35,133+2%

09Lake County, MTMT31,134+17%

10Lincoln County, MTMT19,677+4%

11Park County, MTMT17,191+10%

12Hill County, MTMT16,309−2%

13Glacier County, MTMT13,778+4%

14Big Horn County, MTMT13,124+4%

15Sanders County, MTMT12,400+21%

16Jefferson County, MTMT12,085+20%

17Custer County, MTMT11,867+1%

18Richland County, MTMT11,491+19%

19Fergus County, MTMT11,446−4%

20Roosevelt County, MTMT10,794+2%

21Carbon County, MTMT10,473+10%

22Deer Lodge County, MTMT9,421+0%

23Beaverhead County, MTMT9,371+2%

24Stillwater County, MTMT8,963+9%

25Dawson County, MTMT8,940−1%

26Madison County, MTMT8,623+26%

27Rosebud County, MTMT8,329−11%

28Valley County, MTMT7,578−1%

29Blaine County, MTMT7,044+0%

30Powell County, MTMT6,946−3%

31Broadwater County, MTMT6,774+54%

32Teton County, MTMT6,226−3%

33Pondera County, MTMT5,898−8%

34Chouteau County, MTMT5,895−1%

35Toole County, MTMT4,971−6%

36Musselshell County, MTMT4,730+5%

37Mineral County, MTMT4,535+17%

38Phillips County, MTMT4,217−8%

39Sweet Grass County, MTMT3,678+2%

40Sheridan County, MTMT3,539−14%

41Granite County, MTMT3,309+17%

42Fallon County, MTMT3,049+7%

43Wheatland County, MTMT2,069−8%

44Judith Basin County, MTMT2,023−13%

45Liberty County, MTMT1,959−9%

46Meagher County, MTMT1,927−0%

47McCone County, MTMT1,729−13%

48Powder River County, MTMT1,694−9%

49Daniels County, MTMT1,661−18%

50Carter County, MTMT1,415+4%

51Garfield County, MTMT1,173−8%

52Prairie County, MTMT1,088−9%

53Wibaux County, MTMT937−12%

54Golden Valley County, MTMT823−21%

55Treasure County, MTMT762−11%

56Petroleum County, MTMT496+1%

SHOWING 1–56 OF 56

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UPDATED 2026-07-15 · DATA: US CENSUS BUREAU DECENNIAL CENSUS