C.R.S. § 31-12-201

(1) When a city or town incorporated prior to July 3, 1877, proceeds to abandon its prior organization and to reorganize under the provisions of part 3 of article 2 of this title, it may include within the boundaries of such reorganized municipality all or any part of contiguous area if: (a) The contiguous area has been laid off or platted in accordance with the provisions of this title; (b) The owner of such area has not constituted the same as an addition to such city or town; (c) The area is not situate within another municipality. (2) In such cases, the boundaries of all of such city or town, including such contiguous territory, shall be set forth in the petition described in part 3 of article 2 of this title, and all registered electors residing within those boundaries shall be entitled to vote at the election to be conducted under the provisions of said part 3 of article 2.