Complex sentence: From the time the fair closed until 1920, the Palace of Fine Arts housed the Field Columbian Museum (now the Field Museum of Natural History, since relocated); in 1933, the Palace building re-opened as the Museum of Science and Industry.
Split into simpler sentences: From the time the fair closed until 1920, the Palace of Fine Arts housed the Field Columbian Museum (now the Field Museum of Natural History, since relocated). In 1933, the Palace building re-opened as the Museum of Science and Industry.