Religious fundamentalism of the kind displayed in the Scopes trial was largely a reaction against certain aspects of modernity. In the 1920s America was changing rapidly, and to many, especially in rural areas, such change threatened their whole way of life. Fundamentalists raged against what they saw as the corrupting influences of modern life exemplified by the movie industry, women's fashion, and even the automobile. In the Roaring Twenties, the United States was becoming more urbanized, and many rural dwellers feared the encroachment of what they saw as corrupt big-city values into their lives and communities.

It wasn't simply Scopes on trial in Tennessee in 1925, nor even Darwin's theory of evolution by natural selection—it was modernity as a whole. To William Jennings Bryan and the townsfolk of Dayton, the Scopes trial was an opportunity to take a stand in an increasingly bitter culture war. Modernity represented everything they feared and loathed: an atomized society where people didn't know their own neighbors; a Hollywood movie industry that promoted values incompatible with Christianity; the rapid spread in automobile ownership giving young people the opportunity to go off and spend time away from the supervision of their families; rampant political corruption of the kind so shamelessly displayed by the Tammany Hall machine in New York; mass immigration from non-English speaking countries; and of course, a growing acceptance of the theory of evolution by natural selection, which directly contradicted the literalist interpretation of scripture by which rural folk had lived their whole lives.

In short, rural America felt under siege from modernity. For centuries rural values had been synonymous with American values as a whole—thrift, hard work, patriotism, and bible-based Protestantism. But as the United States became more urbanized, the values of the city—for good or ill—began to prevail. The Scopes trial was a microcosm of the growing cultural tensions developing between town and country. And the moral—if not legal—victory of Clarence Darrow was an indication of just how much the United States had changed in such a short time, and how much it would continue to change in the ensuing decades.

The 1920s are typically seen as a time when urban areas in the United States were becoming more modernized while rural areas remained traditional.  This was the cause of a great deal of conflict between the two regions and, more generally, between modernizers and people who wanted to retain traditional ways.  The Scopes Monkey Trial is one of the greatest examples of this conflict.

In the 1920s, urban America was changing. Huge numbers of immigrants had flooded to American cities, making them demographically different.  Technology was also changing the cities.  City dwellers had things like electricity and running water and radios and movie theaters.  These were things that set them apart from people in rural areas and which made their lives very different.  As life changed, so did values.  Urban America was a place of jazz and flappers.  It was a place that was moving away from the traditional values that still dominated the countryside. 

The Scopes Trial shows us the differences in values and attitudes.  It took place in Tennessee, which was a rural state.  It took place in a very rural part of the state.  The Tennessee law that banned the teaching of evolution was a law that was meant to uphold traditional religious ideas against the ideas of modern science.  Modernized Americans believed in science and did not believe in the literal truth of the creation story.  However, more traditional, largely rural Americans still did believe in the literal truth of the Bible.  This law was one aspect of their attempt to maintain the supremacy of their beliefs.

The Scopes Trial itself also played up the differences between rural and urban America.  Urban newspaper and radio reporters flocked to Dayton to cover the trial.  Many of them (most particularly H.L. Mencken) portrayed the prosecution and the people of Dayton as backwards and ridiculous.  The media clearly sided with the more modern ideas and thereby helped to propagate the idea that there was a fundamental difference between urban and rural America.

The Scopes Trial came about because America was modernizing and some people did not want that to continue.  It came about because modern, urban America was moving away from traditional religious beliefs while traditional, rural America continued to hold to those beliefs.