Upon the date fixed in the resolution the area annexed shall become a part of the district.

No property within the limits of the territory so annexed shall ever be taxed or assessed to pay any portion of the indebtedness of the district to which it is annexed contracted prior to or existing at the date of annexation; nor shall any such property be released from any taxes or assessments levied against it or from liability for payment of outstanding bonds or warrants issued prior to such annexation.