There are a total of 56 counties in the state of Montana. Among them, Beaverhead County is the oldest one (established in 1864) while Petroleum County is the youngest (established in 1926). With population of 155,634, Yellowstone County is the most populated. The biggest county by land area is Beaverhead County (14,356 km2) and the smallest is Silver Bow County (1,860 km2). Below please see all Montana counties which are listed in alphabetical order.
- Beaverhead County, MT
- Big Horn County, MT
- Blaine County, MT
- Broadwater County, MT
- Carbon County, MT
- Carter County, MT
- Cascade County, MT
- Chouteau County, MT
- Custer County, MT
- Daniels County, MT
- Dawson County, MT
- Deer Lodge County, MT
- Fallon County, MT
- Fergus County, MT
- Flathead County, MT
- Gallatin County, MT
- Garfield County, MT
- Glacier County, MT
- Golden Valley County, MT
- Granite County, MT
- Hill County, MT
- Jefferson County, MT
- Judith Basin County, MT
- Lake County, MT
- Lewis and Clark County, MT
- Liberty County, MT
- Lincoln County, MT
- Madison County, MT
- McCone County, MT
- Meagher County, MT
- Mineral County, MT
- Missoula County, MT
- Musselshell County, MT
- Park County, MT
- Petroleum County, MT
- Phillips County, MT
- Pondera County, MT
- Powder River County, MT
- Powell County, MT
- Prairie County, MT
- Ravalli County, MT
- Richland County, MT
- Roosevelt County, MT
- Rosebud County, MT
- Sanders County, MT
- Sheridan County, MT
- Silver Bow County, MT
- Stillwater County, MT
- Sweet Grass County, MT
- Teton County, MT
- Toole County, MT
- Treasure County, MT
- Valley County, MT
- Wheatland County, MT
- Wibaux County, MT
- Yellowstone County, MT
Map of Montana Counties
