Beaverhead County (1864 - Present)
Big Horn County (1864 - Present)
Big Horn County (1913 - Present)
Blaine County (1912 - Present)
Broadwater County (1897 - Present)
Carbon County (1895 - Present)
Carter County (1917 - Present)
Cascade County (1887 - Present)
Choteau County (1864 - Present)
Daniels County (1920 - Present)
Dawson County (1864 - Present)
Deer Lodge County (1864 - Present)
Edgerton County (1865 - Present)
Fallon County (1913 - Present)
Fergus County (1886 - Present)
Flathead County (1893 - Present)
Gallatin County (1865 - Present)
Garfield County (1919 - Present)
Glacier County (1919 - Present)
Golden Valley County (1920 - Present)
Granite County (1893 - Present)
Hill County (1912 - Present)
Jefferson County (1864 - Present)
Judith Basin County (1920 - Present)
Lake County (1923 - Present)
Liberty County (1920 - Present)
Lincoln County (1909 - Present)
Madison County (1864 - Present)
Mccone County (1919 - Present)
Meagher County (1866 - Present)
Mineral County (1914 - Present)
Missoula County (1860 - Present)
Musselshell County (1911 - Present)
Musselshell County Original (1866 - 1867)
Park County (1887 - Present)
Petroleum County (1925 - Present)
Phillips County (1915 - Present)
Pondera County (1919 - Present)
Powder River County (1919 - Present)
Powell County (1901 - Present)
Prairie County (1915 - Present)
Ravalli County (1893 - Present)
Richland County (1914 - Present)
Roosevelt County (1919 - Present)
Rosebud County (1901 - Present)
Sanders County (1906 - Present)
Sheridan County (1913 - Present)
Silver Bow County (1881 - Present)
Stillwater County (1913 - Present)
Sweet Grass County (1895 - Present)
Teton County (1893 - Present)
Toole County (1914 - Present)
Treasure County (1919 - Present)
Valley County (1893 - Present)
Wheatland County (1917 - Present)
Wibaux County (1914 - Present)
Yellowstone County (1883 - Present)