Final answer:
The newspaper headlines would most likely appear in the Roaring 20's era of U.S. history.
Step-by-step explanation:
The newspaper headlines provided indicate events and phenomena that are characteristic of the Roaring 20's era in U.S. history. This was a time of economic growth, cultural change, and technological advancements. The mention of Henry Ford's assembly line, Lucky Lindy's transatlantic flight, the Monkey Trial, and the rise of flappers are all emblematic of the societal changes and innovations that occurred during the 1920s.
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