C.R.S. § 38-52-101: Colorado coordinate system zones defined.

(1) The systems of plane coordinates which have been established by the national ocean service/national geodetic survey (formerly the United States coast and geodetic survey) or its successors for defining and stating the geographic positions or locations of points on the surface of the earth within the state of Colorado are, on and after July 1, 1988, to be known and designated as the Colorado coordinate system of 1927 and the Colorado coordinate system of 1983.

(2) For the purpose of the use of these systems, the state is divided into a north zone, a central zone, and a south zone.

(3) The area now included in the following counties shall constitute the north zone: Moffat, Routt, Jackson, Larimer, Weld, Logan, Sedgwick, Rio Blanco, Grand, Boulder, Gilpin, Adams, Morgan, Washington, Phillips, and Yuma.

(4) The area now included in the following counties shall constitute the central zone: Garfield, Eagle, Summit, Clear Creek, Jefferson, Denver, Arapahoe, Lincoln, Kit Carson, Mesa, Delta, Pitkin, Gunnison, Lake, Chaffee, Park, Fremont, Teller, Douglas, El Paso, Elbert, and Cheyenne.

(5) The area now included in the following counties shall constitute the south zone: Montrose, Ouray, Hinsdale, Saguache, Custer, Pueblo, Crowley, Kiowa, San Miguel, San Juan, Mineral, Rio Grande, Alamosa, Huerfano, Otero, Bent, Prowers, Dolores, Montezuma, La Plata, Archuleta, Conejos, Costilla, Las Animas, and Baca.