Late 1910s-Late 1920s: Because of technological advances in farming, many farm workers lose their jobs, while many farms experience crop surpluses. However, the surpluses lead to lower crop prices, which cause many farms to struggle financially. Displaced farm workers and farmers head to already crowded cities to seek their fortunes there.

Today: The majority of people continue to live in cities or in the large suburban areas that surround them. Farming is one of the least popular vocations, and many tasks traditionally performed by the farmer are now handled by machines.

Late 1910s-Late 1920s: Following World War I, the New York Stock Exchange experiences a surge in speculative investing by ordinary Americans, prompting inflated stock prices and making many Americans wealthy. Many people borrow their investment money on margin, intending to pay it back with their stock profits. When the stock market crashes in...