Colo. Rev. Stat. § 30-5-165
The boundary line between San Miguel and Dolores counties is hereby established as follows:
Commencing at the common section corner of sections twenty-seven, twenty-eight, thirty-three and thirty-four, township forty-one north, range nine west, New Mexico principal meridian, being the point of intersection of the said line with the west boundary line of the county of San Juan; thence north and west along the summit of the range dividing the waters of the San Miguel and Dolores rivers to the summit of Lone Cone mountain; thence northwesterly to the northeast corner of section twenty-three, township forty-two, north, range thirteen west New Mexico principal meridian; thence westerly following the section lines three miles north of the south boundary line of township forty-two to the west bank of the Dolores river on the boundary line between sections fourteen and twenty-three of said township forty-two north range eighteen west New Mexico principal meridian; thence south along the east boundary line of said section twenty-three to the southwest corner of said section twenty-three; thence west along the section lines two miles north of the south boundary of said township forty-two to the west boundary line of the state of Colorado.
C.R.S. § 30-5-165