1796 April 4:
The former Pleasant River post office was renamed as Columbia (1) post office. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide.)
1876 May 11:
Columbia (1) post office was renamed as Columbia Falls post office. (source: Maine Philatelic Society. 1995. The Post Offices of Maine: A Rarity Guide.)