During the 1920's, some people who lived in the United States did not approve of the changes they have been happening since the end of World War I. These people are called traditionalists (a person who has deep respect for long-held cultural and religious values).
One of the reasons why people were afraid of the changing of culture was the Red Scare. People were afraid that their government was going to change from democracy to communism. Since this happened, many different groups were formed that dedicated their time to protect the way of life that they had before WWI.
A group that formed in 1915 was called the Ku Klux Klan. They believed to preserve their way of life they needed to get rid of African Americans, Catholics, Jews, and other foreign-born people who lived in the United States.
Fundamentalism began gaining popularity through the U.S. because people were so afraid of losing their ways within their religion. People who believed in a religion, such as Islam, Protestant, and Christianity, decided to follow strict guidelines that would make sure they were truly faithful to their beliefs.
Since there were so many different groups of (everyday) people scared of losing their faith and religion to the changing of culture, the government got involved.
In 1925, Tennessee passed an act prohibited the teachings of human evolution within schools. John Scopes, a teacher, decided to fight against this and take the state to trial because the law goes against the "freedom of religion and speech" within the Constitution. William Jennings Bryan fought against Clarence Darrow (the attorney for Scopes) in a courtroom, trying to persuade the judge and jury that the government can/can't get involved with religious teachings.