The Swenson Center has some collections of documents about the Second World War. See for example:
MSS P:31 Richard C. Holtman papers
The collection consists of history papers written by Richard Holtman, World War II letters written by Richard's father, Carl Holtman, to his wife Gladys and son Richard, family genealogy research and a commemorative stamp collection.
MSS P:308 Allan Kastrup collection. The American Swedish News Exchange.
The collection spans from early 1920s up to the 1980s and includes a wide variety of materials which reflects ASNE's efforts in promoting Sweden in America and Allan Kastrup's own interest in Swedish immigrants and their achievements in the United States. The most prominent and inclusive material is the clipping collection which documents Swedish cultural, political and economical developments as portrayed in the American press during 1920s-1960s. The collection also includes extensive correspondence between Hedin and Kastrup, a variety of speeches given by Swedish officials in the United States incl. Prince Bertil's; annual reports of the agency; nearly 100 photos depicting the Swedish Pioneer Centennial in 1948; and information on Sweden's neutrality during WWII.
MSS P:309 Sune Lundberg papers
This collection documents American internees in Sweden during WWII. Over 100 planes crashed or were forced to land in Sweden during the war. Lundberg's extensive research includes personal accounts and correspondence with American pilots landing (and crashing) in Sweden, newspaper clippings, and official documents from both Krigsarkivet in Stockholm and Washington. D.C. The collection also contains extensive information on the delivery of American P-51 Mustangs in Stockholm in 1945 along with personal accounts of pilots flying the planes, newspaper clippings of the event, and other official documents documenting what was named the "Speedy Project.”