Montana Counties by Population (2025)

Top 5 Most Populous Counties

Montana flag Yellowstone County

172,789

Montana flag Gallatin County

129,351

Montana flag Missoula County

123,525

Montana flag Flathead County

117,267

Montana flag Cascade County

84,698

56 Counties

County
2025 Pop. ↓
Area (mi²)
Density
Change (2020)
Yellowstone County172,7892,633664.58%
Gallatin County129,3512,605508.16%
Missoula County123,5252,593484.38%
Flathead County117,2675,0872311.81%
Cascade County84,6982,698310.34%
Lewis and Clark County77,4653,458228.83%
Ravalli County48,8602,3912010.02%
Silver Bow County37,186718525.61%
Lake County34,3081,490239.76%
Lincoln County22,6653,613614.85%
Park County18,2032,80265.69%
Hill County16,5922,89961.97%
Sanders County14,2842,760514.66%
Glacier County13,5272,9955-1.59%
Jefferson County13,4821,657811.04%
Big Horn County12,6014,9983-3.66%
Fergus County11,9724,33934.33%
Custer County11,9553,78330.75%
Carbon County11,7852,048612.18%
Richland County11,0592,0855-4.12%
Beaverhead County10,1615,54328.3%
Madison County10,0593,588316.14%
Deer Lodge County9,931737135.42%
Roosevelt County9,8832,3554-8.5%
Stillwater County9,1811,79751.98%
Dawson County8,8162,3724-1.21%
Broadwater County8,5541,192724.69%
Rosebud County8,1765,0082-1.6%
Valley County7,3384,9261-2.89%
Powell County7,2432,32634.34%
Blaine County6,7534,2282-3.62%
Teton County6,5982,27235.53%
Pondera County6,1911,62545.32%
Chouteau County5,7253,9731-2.95%
Musselshell County5,5861,869317.6%
Toole County5,2451,91535.49%
Mineral County5,2301,220414.49%
Phillips County4,2915,14011.85%
Sweet Grass County3,8351,85624.5%
Granite County3,7911,727214.46%
Sheridan County3,3841,6772-4.41%
Fallon County2,8821,6212-4.85%
Meagher County2,1612,392112.55%
Judith Basin County2,1211,87015%
Wheatland County2,0951,42210.92%
Liberty County1,9741,43011.02%
Powder River County1,7653,29814.07%
Daniels County1,6091,4261-2.72%
McCone County1,6062,6421-7.06%
Carter County1,4483,3400.433.13%
Garfield County1,1974,6770.262.13%
Prairie County1,1201,73712.66%
Wibaux County8768901-6.31%
Golden Valley County8531,17413.9%
Treasure County80897816.46%
Petroleum County6201,6560.3724.25%

Overview of Montana Montana Counties

There are 56 counties in Montana.

The most populous county in Montana is Yellowstone County, home to Billings, which has a population of 160,137. Since the time that the last census was taken in 2010, Yellowstone County has seen an increase in the total population of 7.92%.

The only other counties in Montana with a population of more than 100,000 are:

All four counties have experienced substantial population growth of at least 7%; Gallatin County grew the most with a 24.79% growth rate.

Smallest Counties

The county with the lowest population in Montana is Petroleum County, which has a population of 513 people. Since the last census in 2010, Petroleum County’s population has seen an increase of 4.91%.

Following up after Petroleum County, other small counties in Montana include:

Of these counties, Petroleum County experienced the most significant growth while Prairie County had the most dramatic decline with a growth rate of -8.11%.

Fastest Growing Counties

The county with the most significant growth rate in Montana is Gallatin County, which has seen a population growth of 24.79% since the 2010 census was taken, bringing the population up to 111,876.

Montana has several other counties that have experienced double-digit growth since the census including:

The county with the most significant decline was Toole County with a loss of 9.17%.

Sources

  1. US Census State Population Estimates - Most recent state estimates from the Census Bureau's Population Estimates Program
  2. US Census County Population Estimates - Most recent county estimates from the Census Bureau's Population Estimates Program
  3. American Community Survey (2009 - 2013)
  4. Census QuickFacts
  5. Historical Populations of States and Counties (1790 - 1990)