Since its publication in 1859, Charles Darwin's On the Origin of Species has revolutionized science—and become a perennial focal point in battles over the place of religion in public education. A major victory was won by Tennessee creationists on March 21, 1925, when a law went into effect that banned public school teachers from teaching evolution (which was by then firmly accepted by scientists) in biology classes.

Known as the Butler Act after the Primitive Baptist preacher and Tennessee state representative John Butler who introduced it, this piece of legislation forbade any school receiving state funding from teaching evolutionary theory to its students:

Be it enacted by the General Assembly of the State of Tennessee, That it shall be unlawful for any teacher in any of the Universities, Normals and all other public schools of the State which are supported in whole or in part by the public school funds of the State, to teach any theory that denies the story of the Divine Creation of man as taught in the Bible, and to teach instead that man has descended from a lower order of animals.

The American Civil Liberties Union viewed the law as unconstitutional, and jumped into action. With the ultimate goal being to get the Butler Act in front of the U.S. Supreme Court, step one for the ACLU was finding an upstanding Tennessee educator willing to go to court. 

It didn't take long for ACLU workers to find just who they were looking for in John T. Scopes, a football coach and biology teacher from Dayton, Tennessee.

[The ACLU] approached Scopes... and asked him if biology could be taught without mentioning evolution. Scopes replied that he did not think that was possible, especially as the state-approved biology text discussed evolution. Scopes also told the Dayton boosters that he had conducted a biology review session the previous April and had used the textbook. Presumably, although he could not remember this for certain, he had also discussed evolution. By the end of May, Scopes had been indicted for violating the Butler Act by a special grand jury called by local judge John T. Raulston.

Dubbed "The Monkey Trial" by the press, the courtroom proceedings were almost shockingly quick: after only eight days in court, the jury decided on a 'guilty' verdict in just nine minutes. The sentence? A fine of $100.

A political cartoon skewering Tennessee prosecutor William Jennings Bryan, via American Experience

It was little surprise that the jury returned a 'guilty' verdict: after all, the Scopes case had been a political statement all along, designed to make it all the way to the federal Supreme Court. It didn't make it quite so far—the verdict ended up being overturned by the Tennessee state supreme court—but insofar as bringing the Butler Act to the attention of the country as a whole, the ACLU definitely succeeded.

It wasn't until 1967 that the Butler Act was finally removed from the books in Tennessee—but no science teacher was ever again charged with breaking it.