California Code, Streets and Highways Code - SHC § 27022

Proceedings for the incorporation of a district may be instituted by the adoption of an ordinance by the board of supervisors of each county desiring to form a district or by the electors of each such county under the provisions of law applicable to passage of ordinances by initiative declaring that the county, or part of the county, intends to unite with such other counties as may adopt like ordinances to form the district.

The ordinance need not name the counties to be included in the district, and a general statement in the ordinance that the county adopting it intends to unite with any other counties which may adopt like ordinances to form the district, shall be sufficient.