Colorado Revised Statutes Title 30. Government County § 30-1-101. Classification of counties--fixing fees

(a) The city and county of Denver is a county of the first class;

(b) The counties of Adams, Arapahoe, Boulder, Douglas, El Paso, Jefferson, Pueblo, and Weld are counties of the second class;

(c) The counties of Delta, Garfield, Larimer, Las Animas, Logan, Mesa, Montezuma, Montrose, Morgan, and Otero are counties of the third class;

(d) The counties of Alamosa, Archuleta, Bent, city and county of Broomfield, Chaffee, Cheyenne, Clear Creek, Conejos, Costilla, Crowley, Eagle, Elbert, Fremont, Gilpin, Gunnison, Huerfano, Kit Carson, Lake, La Plata, Lincoln, Ouray, Park, Phillips, Prowers, Rio Grande, Routt, Saguache, San Miguel, Sedgwick, Teller, Washington, and Yuma are counties of the fourth class;

(e) The counties of Baca, Custer, Dolores, Grand, Hinsdale, Jackson, Kiowa, Mineral, Moffat, Pitkin, Rio Blanco, San Juan, and Summit are counties of the fifth class.