Colo. Rev. Stat. § 30-5-129
The county of Gunnison is hereby created and established, with the legal capacity and functions of other counties of this state, and with boundaries as follows:
Commencing at a point on the south line of Lake county where the said line crosses the summit of the range of mountains forming the watershed between the waters of the Arkansas river and the streams draining westward into the Colorado river, known as the Saguache range; thence northward, along the summit of such range, to the north line of said Lake county; thence due west to the western line of the state; thence south along the west line of the state to the point where the north line of the county of Ouray intersects the same; thence east along the north line of Ouray county and the north line of Hinsdale county, to the west line of Saguache county; thence north along said west line to the northwest corner of Saguache county; thence east along the north line of Saguache county to the place of beginning.
C.R.S. § 30-5-129