National ZIP Code Advocacy Coalition

The City of Castle Pines currently shares its primary Zoning Improvement Plan (ZIP) code, 80108, with adjacent unincorporated county communities and a neighboring municipality. The ZIP code is shared with other locations because the United States Postal Service (USPS) maps boundaries based on logistical delivery efficiency rather than municipal city borders. This can cause significant real-world challenges for residents and local businesses. When municipalities share mailing designations, online databases can route local sales taxes directly to neighboring towns, first responder routing systems face unnecessary delay risks due to overlapping street names, and homeowner auto and property insurance premiums can be artificially inflated.

What is the National ZIP Code Advocacy Coalition?

The National ZIP Code Advocacy Coalition is a collaborative working group comprised of more than 80 municipalities from across 30 states. Founded in 2023 through a joint effort between the cities of Castle Pines, Colorado and Eastvale, California, the coalition brings together communities facing postal boundary hurdles.

Rather than navigating this issue individually, member cities pool their collective resources, political connections, and spatial data to lobby federal representatives in Washington, D.C. The coalition advocates for structural changes to how the USPS establishes boundary lines for fast-growing and distinct suburban communities.

Municipal membership status across the U.S.

The map below shows the status of municipalities participating in the National ZIP Code Advocacy Coalition across all 50 states. Click on the map to explore the locations of municipal members.