1939 is widely considered the greatest year in Hollywood history. Back then, writes 1939: The Year in Movies author Tom Flannery, the so-called “Big Eight” major American studios “had a combined 590 actors, 114 directors and 340 writers under contract, each of whom worked an eight-hour shift every weekday,” plus half a day on Saturday. “It took an average of 22 days to shoot a movie, at an average cost of $300,000.” Annual grosses exceeding $700 million “made it easier to take a chance on ‘risky’...