Seattle was established as a sub port in August 1941 relieving San Francisco of its historic role in Alaskan supply. Seattle would later develop to include its own sub-ports, including an important one at the terminus of the Canadian National Railway at Prince Rupert, British Columbia, and become an independent port of embarkation in January 1942. A sub port was developed at Portland, Oregon operating under SFPOE until transferred in November 1944 to the Seattle POE.
Seattle's role as a sub port for Alaskan supply relief began in August 1941, relieving San Francisco of its historic role. It later developed its own sub-ports, including one at Prince Rupert, British Columbia, and became an independent embarkation point in January 1942. Portland, Oregon was initially under SFPOE but transferred to the Seattle POE in November 1944.