Warnings from the 1920s: the KKK, Tariffs, and the Devolution of Trade Wars into a World War

In 1925, the Ku Klux Klan marched down Pennsylvania Avenue in Washington, D.C., in a demonstration the Washington Post called "one of the greatest demonstrations this city has ever known." Estimates of participants ranged from 30,000 to 60,000. The marchers protested what they saw as foreign threats to their way of life: immigrants and imported goods they claimed were polluting their country.

The 1920s were marked by economic growth. GDP rose steadily, and the stock market climbed—first at a steady pace, then spectacularly in the latter half of the decade. Yet, many Americans remained angry, convinced that their struggles stemmed from “them”: immigrants and foreign producers. Feeding this resentment was a new form of media—radio.

In 1923, only about 1% of American households owned a radio. By 1931, more than half did. This rapid adoption made radio a powerful tool for spreading fear and fueling the resurgence of extremist groups like the KKK. Voices on the airwaves amplified suspicions of "outsiders," heightening nativist and isolationist sentiment.

Politicians responded. In 1924, a year before the KKK marched in D.C., Congress passed the Immigration Act of 1924 (Johnson-Reed Act). The law slashed immigration quotas to 2% of each nationality based on the 1890 census—a deliberate choice to limit newcomers from Southern and Eastern Europe. It also effectively banned immigration from Asia. On the economic front, a series of tariff bills raised barriers to foreign imports. The Smoot-Hawley Tariff Act of 1930 escalated this trend, imposing duties of 40-48% on over 20,000 imported goods. Despite warnings from over 1,000 economists and 24 foreign nations, President Hoover signed the bill, triggering retaliatory tariffs that further strangled global trade.
By the time the Great Depression hit, Hoover presided over an economy in freefall. Unemployment soared to 25%, and GDP was cut in half. Meanwhile, Europe—still reeling from the devastation of World War I—sank deeper into economic and political chaos. Chronic unemployment and inflation gave rise to extremist movements, most notably in Germany. The Great Depression brought Hitler and FDR to power within five weeks of each other in early 1933.

The protectionist sentiment of the 1920s wasn’t limited to the U.S. or Europe. Across the globe, nations turned inward. Japan, angered by a Chinese boycott of its goods, attacked Shanghai in 1932. For the first time on a large scale, bombs rained down on civilians, setting the stage for the Pacific theater of World War II. This chain of events culminated in Japan bombing Pearl Harbor and the U.S. entering a global conflict that would claim over 100 million lives.

How did the U.S. transform the Roaring Twenties into the Great Depression and World War II? In part, by turning fear of others into policy. Efforts to isolate the U.S. from the world—through immigration restrictions and protectionist tariffs—did not insulate the country. Instead, they contributed to a collapse of global trade that turned the exchange of goods into the exchange of bads: insults, bombs, and bullets. Modern nations will almost inevitably trade. The only question is whether they will trade goods—products, people, investments, and services—or bads—conflict, poverty, and obstacles to prosperity.

A century later, we can still draw lessons from the 1920s.