Montana Counties by Population (2026)

2026 Pop.

20K

40K

60K

80K

100K

120K

140K

160K

Top 5 Most Populous Counties

56 Counties

County
2026 Pop. ↓
Area (mi²)
Density
Change (2020)
Yellowstone County173,2952.6K664.89%
Gallatin County129,0942.6K507.93%
Missoula County124,2942.6K485.02%
Flathead County116,5915.1K2311.17%
Cascade County84,3192.7K31-0.11%
Lewis and Clark County75,7633.5K226.44%
Ravalli County49,0412.4K2110.41%
Silver Bow County36,016718502.29%
Lake County33,6991.5K237.85%
Lincoln County22,8183.6K615.57%
Park County18,3462.8K76.48%
Hill County15,8332.9K5-2.58%
Sanders County14,2332.8K514.22%
Jefferson County13,7401.7K813.16%
Glacier County13,3553K4-2.83%
Big Horn County12,7385K3-2.64%
Fergus County11,9544.3K34.22%
Custer County11,8663.8K30.03%
Carbon County11,6422K610.73%
Richland County10,8962.1K5-5.53%
Madison County10,2413.6K318.24%
Beaverhead County10,2405.5K29.2%
Deer Lodge County10,063737146.79%
Roosevelt County9,9372.4K4-8.01%
Stillwater County9,8761.8K59.71%
Broadwater County8,7801.2K727.93%
Dawson County8,5532.4K4-4.14%
Rosebud County8,3365K20.36%
Valley County7,3524.9K1-2.76%
Powell County7,1162.3K32.57%
Blaine County6,9414.2K2-0.89%
Teton County6,4542.3K33.21%
Pondera County6,0181.6K42.4%
Chouteau County5,8864K1-0.52%
Musselshell County5,6021.9K317.96%
Mineral County5,3151.2K416.35%
Toole County5,2031.9K34.75%
Phillips County4,1465.1K1-1.54%
Sweet Grass County3,7731.9K22.81%
Granite County3,6761.7K211.19%
Sheridan County3,3641.7K2-4.86%
Fallon County2,8401.6K2-6.24%
Judith Basin County2,1351.9K15.54%
Meagher County2,0812.4K18.16%
Wheatland County2,0381.4K1-1.64%
Liberty County1,8841.4K1-3.78%
McCone County1,7832.6K13.12%
Powder River County1,7403.3K12.78%
Daniels County1,6231.4K1-1.81%
Carter County1,3973.3K0.42-0.71%
Garfield County1,1114.7K0.24-5.12%
Prairie County1,1061.7K11.47%
Wibaux County9258901-1.18%
Golden Valley County8551.2K14.14%
Treasure County6839781-9.89%
Petroleum County4891.7K0.30-2.59%

Overview of Montana Counties

There are 56 counties in Montana.

Yellowstone County is the largest county in the state, with a population of 173,295. The most recent census shows that its population has increased by 0.05% since the previous census.

A number of other Montana counties also boast relatively large populations for their state, though not able to match the density of Yellowstone County:

Montana Counties with the Fewest Residents

The smallest county in Montana is Petroleum County , with a population of just 489. This total represents a decrease of 0.0% since the last census count was performed.

Other small counties include:

Montana Counties with Rapid Growth

Broadwater County , with its current population of 8,780, has shown the largest population growth, with an increase of 0.3% since the last census.

On the other hand, Treasure County has had the largest decrease in population, with its 683 current residents totalling 0.1% less than the previous census.

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)

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