The prosperity and leisure of the 1920s hid serious social tensions. In the political realm, such tensions exposed themselves in isolationism and anti-immigration policies. Elsewhere in American society, social tensions centered on questions of race, religion, and fundamentalism.

Many blacks, unhappy with the continued slow pace of social advancement, in the 1920s turned to Marcus Garvey and the United Negro Improvement Association (UNIA), which Garvey had moved from Jamaica to the U.S. in 1916. Garvey glorified black culture and founded a chain of UNIA businesses to promote black economic cooperation. Garvey urged American blacks to return to Africa and establish an independent nation. The Garvey movement attracted many followers, with the UNIA claiming 80,000 members, but was sharply criticized by the National Association for the Advancement of Colored People (NAACP) for being too radical. In 1923, Marcus Garvey was found guilty of fraud, and in 1927 he was deported to Jamaica. The UNIA could not survive without his leadership, but it left an important legacy as a prominent African American mass movement.

The NAACP was a more conservative force for social reform. Led by W.E.B. Du Bois, the NAACP called for integration and equal treatment for blacks. In part because of the migration of blacks northward during World War I, membership in the NAACP grew markedly during the early 1920s. Still, lynchings continued in the South, and racist Americans gained influence through organizations such as the Ku Klux Klan.

Nativism and intolerance during the 1920s was seen most prominently in the resurgence of the Ku Klux Klan (KKK) in 1915. The Klan organized a wildly successful membership drive in 1920, with estimates of new recruits as high as five million. Instead of just targeting blacks for attack, as the earlier Klan had done, the new Klan expanded its target to include all non-Protestants. By calling for “100 percent Americanism,” the Klan capitalized on middle-class Protestant dismay at changing social and economic conditions in America. The Klan took root throughout the South, where it mostly targeted blacks, and in parts of the West and Midwest, where Catholics and Jews bore the brunt of Klan intimidation and murder. In some states, the Klan even exerted dominant political, as well as social, force. The Klan collapsed in 1925 after the widespread corruption of Klan leadership was exposed. Membership faded quickly, but the Klan would return after World War II as a significant force.

During the late nineteenth and early twentieth centuries, science challenged the infallibility of religious doctrine. Liberal Protestants accepted the majority of scientific findings and sought to integrate these findings into their religion, but more conservative Protestants refused this strategy. This refusal was known as fundamentalism. Fundamentalists insisted on the divine inspiration and truth of every word in the Bible, and focused in the early 1920s on refuting the theory of evolution. Articulated by Charles Darwin in 1895, evolution contradicted biblical accounts of the creation of man. William Jennings Bryan, former presidential candidate and secretary of state, led a movement to ban schools from teaching evolution. In 1925, the Tennessee legislature did just that, prompting the American Civil Liberties Union (ACLU) to offer to defend any teacher willing to challenge this law. John T. Scopes accepted this offer, broke the law, and was arrested, bringing the issue to court. In the famed Scopes Monkey Trial, Bryan aided the prosecution, and Chicago lawyer Clarence Darrow defended Scopes. The judge would not allow expert testimony, leaving the matter basically up to debate between Darrow and Bryan. In cross-examination, Darrow made a fool of Bryan, exposing the latter’s lack of scientific knowledge. Although Scopes was found guilty, the nation at large, paying close attention to the trial, generally considered the anti-fundamentalist forces to have won the argument.