Included among LAFCOs’ charges are discouraging urban sprawl and encouraging logical and orderly local agency boundaries to promote the efficient extension of municipal services. Since the enactment of the Knox-Nesbitt Act in 1963, unincorporated islands have been a concern for LAFCOs in that islands result in illogical boundaries and difficulty and confusion in the delivery of municipal services. Annexation of islands to cities is usually preferred, as it often results in a higher level of local service for the island residents.

Current LAFCO law encourages and expedites island annexations that promote greater efficiency in providing services to unincorporated areas, especially those that are disadvantaged. In 2012, Contra Costa LAFCO identified 21 island areas that fit the description of islands eligible for an expedited annexation process.