C.R.S. § 31-23-212

The territorial jurisdiction of any commission over the subdivision of land includes all land located within the legal boundaries of the municipality and, limited only to control with reference to a major street plan and not otherwise, also includes all land lying within three miles of the boundaries of the municipality not located in any other municipality; except that in the case of any such land lying within five miles of more than one municipality, the jurisdiction of each commission shall terminate at a boundary line equidistant from the respective municipal limits of such municipalities. The jurisdiction over the subdivision of lands outside the boundary of a municipality shall apply equally to any municipality.