Colo. Rev. Stat. § 30-5-102
Except for those portions that became part of the city and county of Broomfield on November 15, 2001, in accordance with sections 10 to 13 of article XX of the state constitution, all that portion of Arapahoe county, beginning at the northwest corner of Arapahoe county as now constituted, thence east along the north boundary line of said Arapahoe county to the northeast corner of said Arapahoe county, thence south along the east boundary line of said county to the southeast corner of said county, thence west along the south boundary line of said county to the east boundary line of range fifty-seven west, thence north along the said east boundary line to the intersection of the east boundary line of range fifty-seven and the south boundary line of township three in said range, thence west along the south boundary line of township three to the point of intersection of south boundary line of township three in range fifty-seven west, and the east boundary line of the city of Denver as the same is constituted at the time this section takes effect, thence northerly and westerly, following the easterly and northern boundary lines of said city of Denver as then constituted, to the point of intersection of said boundary lines with the west boundary line of Arapahoe county, thence north to the place of beginning, shall be set apart and is hereby established as a county to be called the county of Adams, which said county shall have the legal capacities and functions of other counties of this state.
C.R.S. § 30-5-102