Colo. Rev. Stat. § 30-5-147
The county of Montrose is hereby established with the legal capacity and functions of other counties in this state, and with boundaries as follows:
Beginning at a point on parallel one hundred and seven degrees and thirty minutes two miles south of the third correction line extended west; thence west to a point due south of the mouth of the Rio Dominguez; thence south to parallel thirty-eight degrees and thirty minutes; thence west along said parallel to the west line of the state; thence south along said line to the northwest corner of Ouray county; thence east along said line to parallel one hundred and eight degrees of west longitude; thence north along said last named parallel to a point ten miles due north of the north line of Ouray county; thence east to parallel one hundred and seven degrees and thirty minutes; thence north along said parallel to the point of beginning.
C.R.S. § 30-5-147