Municipal Boundaries (US) uses 2020 data from TomTom as its baseline data source. Source data from official government agencies includes information about annexations, de-annexations, additions, and deletions. This information is sourced from a number of governmental agencies, including but not limited to:
- Offices of secretaries of states
- State boundary commissions
- State planning, economic, and community development agencies
- Revenue departments or state tax commissions
- State transportation departments