If at the election a majority of all those voting upon the question of creation of the district, and a majority of those voting thereon in each city is in favor of the formation of the district, the board of supervisors shall make an order forming the district and thereupon it is formed.
The order shall contain the name of the district and a description of the boundaries, or otherwise indicate its territorial extent.
The order is conclusive evidence of the regularity of all prior proceedings, except the adoption and publication in full of the resolution of intention, and of the fact of the holding of the hearing on formation.