In the notice provided for in RCW 36.12.050, the place selected to be the county seat of the county must be so declared upon a day not more than ninety days after the election. After the day named the place chosen is the seat of the county; and the several county officers, whose offices are required by law to be kept at the county seat, shall remove their respective offices, files, records, office fixtures, furniture, and all public property pertaining to their respective offices to the new county seat.