C.R.S. § 30-5-138

The county of La Plata shall be bounded as follows: Commencing at a point six miles west of the mouth of Lost Trail creek, and running thence north to a point ten miles north of the thirty-eighth parallel of north latitude; thence west to the western boundary of the state; thence south along said western boundary to the southwest corner of the state; thence east along the southern boundary of the state to a point due south of the place of beginning; thence north to the place of beginning.