Sigrid (Christiane Seidel) claims "Syttende mai" (May 17) is the celebration of when Norway became free from the Danes. This is incorrect; it is the celebration of the signing of the Norwegian Constitution on May 17, 1814.
A catastrophic explosion indeed occurred in Atlantic City, but not in the time period depicted in this episode. In 1937 10,000 gallons of gasoline exploded in Atlantic City, threatening the resorts.