The corporate limits of the City of Lincolnton shall be those existing at the time of ratification of this charter, as the same are set forth on an official map of the City, and as the same may be altered from time to time in accordance with law. An official map showing the current boundaries of the City, entitled "Map of the City of Lincolnton, North Carolina," or a current metes and bounds description of the corporate limits shall be maintained in the office of the City Clerk, and shall be available for public inspection. Upon alteration of the corporate limits made pursuant to law, the appropriate changes to the official map of the City shall be made.