Adams County (1902 - Present)
Alamosa County (1913 - Present)
Arapahoe County (1861 - Present)
Archuleta County (1885 - Present)
Baca County (1889 - Present)
Bent County (1870 - Present)
Boulder County (1861 - Present)
Broomfield County (2001 - Present)
Carbonate County (1879 - 1879)
Chaffee County (1879 - Present)
Cheyenne County (1889 - Present)
Clear Creek County (1861 - Present)
Costilla County (1861 - Present)
Crowley County (1911 - Present)
Custer County (1877 - Present)
Delta County (1883 - Present)
Denver County (1902 - Present)
Dolores County (1881 - Present)
Douglas County (1861 - Present)
Eagle County (1883 - Present)
El Paso County (1861 - Present)
Elbert County (1874 - Present)
Fremont County (1861 - Present)
Garfield County (1883 - Present)
Gilpin County (1861 - Present)
Grand County (1874 - Present)
Greenwood County (1870 - 1874)
Guadaloupe County (1861 - Present)
Gunnison County (1877 - Present)
Hinsdale County (1874 - Present)
Huerfano County (1861 - Present)
Jackson County (1909 - Present)
Jefferson County (1861 - Present)
Kiowa County (1889 - Present)
Kit Carson County (1889 - Present)
La Plata County (1874 - Present)
Lake County (1861 - Present)
Larimer County (1861 - Present)
Las Animas County (1866 - Present)
Lincoln County (1889 - Present)
Logan County (1887 - Present)
Mesa County (1883 - Present)
Mineral County (1893 - Present)
Moffat County (1911 - Present)
Montezuma County (1889 - Present)
Montrose County (1883 - Present)
Morgan County (1889 - Present)
Otero County (1889 - Present)
Ouray County (1877 - Present)
Park County (1861 - Present)
Phillips County (1889 - Present)
Pitkin County (1881 - Present)
Platte County Proposed (1872 - 1872)
Prowers County (1889 - Present)
Pueblo County (1861 - Present)
Rio Blanco County (1889 - Present)
Rio Grande County (1874 - Present)
Routt County (1877 - Present)
Saguache County (1866 - Present)
San Juan County (1876 - Present)
San Miguel County (1883 - Present)
Sedgwick County (1889 - Present)
Summit County (1861 - Present)
Teller County (1899 - Present)
Uncompahgre County (1883 - 1883)
Washington County (1887 - Present)
Weld County (1861 - Present)
Yuma County (1889 - Present)