The Portland Waterfront Historic District was listed in the National Register of Historic Places on May 2, 1974 for its significance at the local level in the areas of architecture, commerce, transportation and community planning and development. On December 23, 1984 additional properties were added to the district and the boundary expanded at both the east and west ends of the district. The purpose of the current nomination was to again increase the boundaries to include two more buildings and a granite bulkhead on the south side of Commercial Street. The buildings are the Twitchell-Champlin Co. building erected between 1884 and 1924 as a spice mill, candy factory, and cannery, and the Armour & Company meat packing plant erected about 1900. Both buildings are located Merrill?s Wharf, an earth-filled wharf with two granite block bulkheads, built between 1830 and 1850, prior to the establishment of Commercial Street. The building and wharf are contiguous to the existing district and are of significant importance to the economic, industrial, transportation, and commercial history of the Portland waterfront. This nomination also changes and elongates the period of significance for the district from the ?19th century? to a more specific ?c. 1790 to 1936,? which encompasses the construction dates for contributing resources within both the expanded and existing district boundaries. Finally, in recognition of the important role that meat packing, food processing and canning facilities had on the growth of the city and the state, industry was recognized as an area of significance.