Colo. Rev. Stat. § 30-5-105
All that part of the county of Conejos included within the following described boundaries shall be set apart and is hereby established as a county, to be called the county of Archuleta, the boundaries of which are as follows:
Beginning on the southern boundary line of the state of Colorado at the intersection of said state line and the eastern boundary line of Tierra Amarilla Grant, which is thirty-seven and eleven one-hundredths chains west on said state line from the range line between ranges four and five east of the New Mexico principal meridian, and thence in a northwesterly direction following said east boundary line of the said Tierra Amarilla Grant to the north corner of said Tierra Amarilla Grant, and thence in the same direction until said line intersects with the range line between ranges two and three east of the New Mexico principal meridian, and thence north following said range line to the north boundary line of the county of Conejos, thence west along the southern boundary of the county of Mineral and the county of Hinsdale to the southwest corner of the said county of Hinsdale, thence south to the state line and thence east along the said southern boundary line of the state of Colorado to the place of beginning.
C.R.S. § 30-5-105