marriage is widely believed to have been a success due in large part to their genuine mutual love. They had three children: Ragnhild (1930–2012); Astrid (b. 1932); and the much awaited heir, Harald (b. 1937). Crown Princess Märtha soon became a popular and respected member of the royal family, later undertaking a range of official engagements and she also gave many speeches, unusual for royal females in that era. Crown Prince Olav and Crown Princess Märtha of Norway resided at the country estate of Skaugum, which was a wedding gift from Baron Fritz Wedel Jarlsberg. When the main house at Skaugum was destroyed by fire in 1930, the Crown Princess took active involvement in its rebuilding. Tragedy struck Crown Princess Märtha in 1935 when her sister, the Queen of the Belgians, was killed in a car crash; the two siblings had been very close. Later King Olav said that it took his wife more than ten years to come to terms with her sister's death, and he did not think that she ever really got over it. She – together with her elder sister Margaretha – became a great support for her sister's children in Belgium. In 1939, shortly before the outbreak of World War II, the Crown Prince and Princess visited the United States. The couple befriended President Franklin Roosevelt and his wife, Eleanor. During this visit, the royal couple conducted an extensive tour of the Upper Midwest, where many Norwegian immigrants were settled. Also during their US tour, Crown Princess Märtha was initiated, together with her lady-in-waiting Ragni Østgaard, into the Delta Zeta sorority being pinned at the University of North Dakota by Delta Zeta national president Myrtle Graeter Malott. In 1938 upon the death of her mother-in-law, Queen Maud, Crown Princess Märtha became the royal Norwegian court's senior lady. World War II Crown Princess Märtha contributed greatly towards Norway mobilizing for self-defence by making a public announcement on 26 January 1940 when she encouraged Norwegian women to participate in the mobilization work. During the flight from the German invasion in 9–10 April 1940, the Norwegian government decided that the Crown Princess and her children were to flee across the border to her native Sweden while her husband and father-in-law remained. Upon their arrival at the Swedish border, they were first denied entry because they could not provide passports; she then instructed her driver to run through the