California Code, Health and Safety Code - HSC § 6465

If a majority of the votes cast in each county are in favor of formation of the district, the board of supervisors shall make and cause to be entered in its minutes an order that a district of the name and with the boundaries stated in the order calling the election, setting forth the boundaries, has been established.

The board shall immediately file for record in the office of the county recorder of each county within which the district is located a certified copy of the order declaring the district established.

The order is conclusive evidence of the fact and regularity of all prior proceedings required by this part or by law, and of the existence and validity of the district.