In such decree the department shall designate the place, prayed for in the petition, where the office or principal place of business of the district shall be located, which shall be within the corporate limits of the district. It may be changed by order of the department from time to time, upon the application of the board of directors of said district. The regular meetings of the board shall be held at such office or place of business, but for cause may be adjourned to any convenient place. The official records and files of the district shall be kept at the office so established.