Colorado state statutes require municipalities to adopt a "Three-Mile Plan" for their communities.  The purpose of this plan is to indicate in a general way how a City envisions areas outside their boundaries developing in the future if they were to be annexed.  This plan is required prior to a municipality annexing any land.  Such plan may extend up to three miles from the municipality's boundary. 

State statutes also indicate that the plan shall generally describe the location, character, extent of streets, parks, open space, public utilities and proposed land uses.  The Plan is generally adopted as an addendum to the City's Comprehensive Plan.