The corporate limits shall be those existing at the time of ratification of this Charter, as set forth on the official map of the City and as they may be altered from time to time in accordance with law. An official map of the City, showing the current boundaries, shall be maintained permanently in the office of the City Clerk and shall be available for public inspection. Immediately upon alteration of the corporate limits made pursuant to law, the appropriate changes of the official map shall be made and copies shall be filed in the office of the Secretary of State, the Gaston County Register of Deeds and the appropriate board of elections.