Sonja Graf-Stevenson (1914-1965) was the winner of four U.S. Women's Opens and two Closed Championships (1957 – tied with Gresser, 1964). She was woman champion of her native Germany until the outbreak of World War II. At the world women’s championship tournament in Buenos Aires in 1939, she was prevented from playing for Germany by a Nazi edict. She went on to play at large under the banner of "Liberty." She took 2nd place with a 16-3 score, behind Menchik (who had an 18-1 score). In the 1930s she was considered the second best woman chess player in the world, after Vera Menchik. Both Vera Menchik and Sonja Graf married a chess player named Stevenson. She learned the game at age four and was a pupil of Dr. Siegbert Tarrasch. In 1957, she won the California Women’s Chess Championship.