The Legion of Honor was the gift of Alma de Bretteville Spreckels, wife of the sugar magnate and thoroughbred racehorse owner/breeder Adolph B. Spreckels. The building is a full-scale replica, by George Applegarth and Henri Guillaume, of the French Pavilion at the 1915 Panama–Pacific International Exposition, which in turn was a three-quarter-scale version of the Palais de la Légion d'Honneur (also known as the Hôtel de Salm) in Paris, by Pierre Rousseau (1782). At the close of the exposition, which was located just a few miles away, the French government granted Spreckels permission to construct a permanent replica of the French Pavilion. World War I delayed the groundbreaking until 1921. Dedicated as a memorial to California soldiers killed in the war, the museum opened on Armistice Day, November 11, 1924.