A county island is an area of unincorporated land which is completely surrounded by a city or town. County islands are created when a city or town annexes land into their corporate boundaries but excludes certain areas. Those excluded areas that remain under county jurisdiction are referred to as county islands.People who live in county islands usually don't receive services from the city which surrounds them.n Maricopa County, where most of Greater Phoenix is located, there are people who might receive their mail at an address that says Scottsdale or Gilbert because those post offices service those areas, but they really don't live in those cities. They live in county islands.