Complex sentence: The California Palace of the Legion of Honor, which was championed by his wife Alma and paid for from the Spreckels fortune, and the M. H. de Young Memorial Museum were merged in 1972 to become the Fine Arts Museums of San Francisco.
Split into simpler sentences: The California Palace of the Legion of Honor was championed by his wife Alma and paid for from the Spreckels fortune. It was merged with the M. H. de Young Memorial Museum in 1972 to become the Fine Arts Museums of San Francisco.