The majority of Portland's non-passenger terminals are for petroleum products, especially the Portland–Montreal pipeline, which has gradually reduced its capacity since 2010.

During World War II, Battery Steele was constructed in Portland on Peaks Island, making Fort Preble obsolete.

Battery Steele itself was abandoned after the war ended.From 1970 to 2008 the Port of Portland was connected by a seasonal (summer only) international ferry service to Yarmouth, Nova Scotia.

Bay Ferries began operating the high speed catamaran HSC The Cat on the Portland-Nova Scotia route in 2006 using the newly constructed Ocean Gateway International Marine Passenger Terminal for the 2008 and 2009 seasons.

[13] The construction of a cold storage facility has been proposed several times, most recently in 2020, as a way to make the port more valuable for foreign trade.