Annexation is a procedure for bringing unincorporated areas into a city, town, or additional service areas into a special purpose district. An annexation area is usually adjacent to an incorporated city, town, or a special purpose district. Washington State law governs the procedures for annexation. The Annexation Handbook for Cities and Towns in Washington State, Report No. 19, is on file with the Municipal Research and Services Center and provides information on the annexation process.

Five Methods of Annexation

Annexations may be accomplished through a variety of ways, including: 

  • Election
  • Direct petition (60%)
  • 50/50 direct petition
  • Annexation of small unincorporated islands
  • Annexation by interlocal agreement.  

For more information, refer to the Common Methods of Annexation page.

Once an area is annexed to a city, the city replaces the county as the primary provider of local government and urban services (e.g., police, animal control, zoning and land use, etc.). Once an area is annexed to a district, the district replaces the current provider with a specific service (e.g., sewer, water, fire, etc.).

Annexation-Related Interlocal Agreements (ILAs)

An interlocal agreement is a common method for neighboring jurisdictions to cooperate with one another. For the purposes of annexation, an interlocal agreement can be used to draft the procedure of an annexation and to draft an agreement for transition of services or governmental activities such as road maintenance, fire protection services, law enforcement services, court services, or emergency dispatch services. Snohomish County has several existing annexation-related interlocal agreements with individual cities (see Related Interlocal Agreements page for details).  

Annexation Resources - Snohomish County

Other Resources

Additional Information

If you have questions regarding annexations or interlocal agreements, contact Snohomish County Planning and Development Services at 425-388-3311.