Clarence Darrow was born in rural northeastern Ohio on April 18, 1857. He was the son of Amirus Darrow and Emily (Eddy) Darrow. Both the Darrow and the Eddy farms had deep roots in colonial New England, and several of Darrow's ancestors served in the American Revolution. Clarence's father was an ardent abolitionist and a proud iconoclast and religious freethinker, known in town as the "village infidel." Emily Darrow was an early supporter of female suffrage and a women's rights advocate. Clarence attended Allegheny College and the University of Michigan Law School but did not graduate from either institution. He was admitted to the Ohio bar in 1878. The Clarence Darrow Octagon House, which was his childhood home in the small town of Kinsman, Ohio, contains a memorial to him.
Darrow began his career reading law in Youngstown, Ohio, where he was first admitted to the profession by Judge Alfred W. Mackey. He opened his first practice in Andover, Ohio, and then moved to Ashtabula, where he became involved in Democratic Party politics and served as the town counsel. In 1880 he married Jessie Ohl, and seven years later he moved to Chicago with his wife and young son, Paul. There, he worked for the city government as a lawyer and made a mark for himself speaking at Democratic rallies and other speaking engagements. He was a close friend and protege of Illinois Gov. John Altgeld and helped secure a pardon from the governor for the anarchists who were imprisoned for the Haymarket Square bombing. With Altgeld's help, Darrow became a corporate lawyer for the Chicago & Northwestern Railway Company, a major Midwestern railroad. In 1894 Darrow represented Eugene V. Debs, the leader of the American Railway Union, who was prosecuted by the federal government for leading the Pullman Strike of 1894. Darrow severed his ties with the railroad to represent Debs, making a financial sacrifice. He saved Debs in one trial but could not keep the union leader from being jailed in another.
Also in 1894, Darrow took on the first murder case of his career, defending Patrick Eugene Prendergast, the "mentally deranged drifter" who had confessed to murdering Chicago mayor Carter H. Harrison, Sr. Darrow's "insanity defense" failed and Prendergast was executed that same year. Among fifty defenses in murder cases throughout the whole of Darrow's career, the Prendergast case would prove to be the only one resulting in an execution.
Darrow became one of America's leading labor attorneys. He helped organize the Populist Party in Illinois and then ran for Congress as a Democrat in 1896 but lost to Hugh R. Belknap. In 1897 his marriage ended in divorce. He represented the woodworkers of Wisconsin in a notable case in Oshkosh in 1898 and the United Mine Workers in Pennsylvania in the great anthracite coal strike of 1902. He flirted with the idea of running for mayor of Chicago in 1903 but ultimately decided against it. That year he married Ruby Hammerstrom, a young Chicago journalist.
From 1906 to 1908, Darrow represented the Western Federation of Miners leaders William "Big Bill" Haywood, Charles Moyer, and George Pettibone when they were arrested and charged with the 1905 murder of former Idaho Gov. Frank Steunenberg. After a series of trials, Haywood and Pettibone were found not guilty and the charges were dropped against Moyer.
In 1911, the American Federation of Labor called on Darrow to defend the McNamara brothers, John and James, who were charged with dynamiting the Los Angeles Times building on October 1, 1910, during the bitter struggle over the open shop in Southern California. Owing to a faulty timer, the bomb detonated prematurely, when the Times building was still occupied by employees. The bomb had been placed in an alley behind the building, and although the explosion itself did not bring the building down, it ignited nearby ink barrels and natural gas main lines. In the ensuing fire, 21 people were killed. The AFL appealed to local, state, regional and national unions to donate 25 cents per capita to the defense fund, and set up defense committees in larger cities throughout the nation to take donations.
In the weeks before the jury was seated, Darrow became increasingly concerned about the outcome of the trial and began negotiations for a plea bargain to spare the defendants' lives. During the weekend of November 19–20, 1911, he discussed with pro-labor journalist Lincoln Steffens and newspaper publisher E. W. Scripps the possibility of reaching out to the Times about the terms of a plea agreement. The prosecution had demands of its own, however, including an admission of guilt in open court and longer sentences than the defense proposed.
The defense's position weakened when, on November 28, Darrow was accused of orchestrating to bribe a prospective juror. The juror reported the offer to police, who set up a sting and observed the defense team's chief investigator, Bert Franklin, delivering $4,000 to the juror two blocks away from Darrow's office. After making payment, Franklin walked one block in the direction of Darrow's office before being arrested right in front of Darrow himself, who had just walked to that very intersection after receiving a phone call in his office. With Darrow himself on the verge of being discredited, the defense's hope for a simple plea agreement ended.  On December 1, 1911, the McNamara brothers changed their pleas to guilty, in open court. The plea bargain Darrow helped arrange got John fifteen years and James life imprisonment. Despite sparing the brothers the death penalty, Darrow was accused by many in organized labor of selling the movement out.
Two months later, Darrow was charged with two counts of attempting to bribe jurors in both cases. He faced two lengthy trials. In the first, defended by Earl Rogers, he was acquitted. Early during the second trial Rogers resigned after a disagreement with Darrow over defense strategy; Darrow served as his own attorney for the remainder of the trial, which ended with a hung jury. A deal was struck in which the D.A. agreed not to retry Darrow if he promised not to practice law again in California. Darrow's early biographers—Irving Stone and Arthur & Lila Weinberg—asserted that he was not involved in the bribery conspiracy; but more recently Geoffrey Cowan and John A. Farrell, with the help of new evidence, concluded that he almost certainly was
As a consequence of the bribery charges, most labor unions dropped Darrow from their list of preferred attorneys. This effectively put Darrow out of business as a labor lawyer, and he switched to civil and, most notably, criminal cases. "He began taking criminal cases, because he had become convinced that what we are used to describing as 'the criminal-justice system' was a gigantic fraud that ruined real people's lives because they had no representation capable of defending them properly against it."
Throughout his career, Darrow devoted himself to opposing the death penalty, which he felt to be in conflict with humanitarian progress. In more than 100 cases, Darrow only lost one murder case in Chicago. He became renowned for moving juries and even judges to tears with his eloquence. Darrow had a keen intellect often hidden by his rumpled, unassuming appearance.
A July 23, 1915, article in the Chicago Tribune describes Darrow's effort on behalf of J.H. Fox, an Evanston, Illinois, landlord, to have Mary S. Brazelton committed to an insane asylum against the wishes of her family. Fox alleged that Brazelton owed him rent money, although other residents of Fox's boarding house testified to her sanity.
In the summer of 1924, Darrow took on the case of Leopold and Loeb, the teenage sons of two wealthy Chicago families who were accused of kidnapping and killing Bobby Franks, a 14-year-old boy from their stylish Kenwood neighborhood. Nathan Leopold was 19 and Richard Loeb was 18 when they were arrested. Leopold was a law student at the University of Chicago about to transfer to Harvard Law School. Loeb was the youngest graduate ever from the University of Michigan. When asked why they committed the crime, Leopold told his captors: "The thing that prompted Dick to want to do this thing and prompted me to want to do this thing was a sort of pure love of excitement... the imaginary love of thrills, doing something different... the satisfaction and the ego of putting something over."
The Chicago newspapers labeled the case the "Trial of the Century" and Americans around the country wondered what could drive the two young men, blessed with everything their society could offer, to commit such a depraved act.
The killers were arrested after a passing workman spotted the victim's body in an isolated nature preserve near the Indiana border just half a day after it was hidden, before they could collect a $10,000 ransom. Nearby were Leopold's eyeglasses with their distinctive, traceable frames, which he had dropped at the scene.
Leopold and Loeb made full confessions and took police on a grim hunt around Chicago to collect the evidence that would be used against them. The state's attorney told the press that he had a "hanging case" for sure. Darrow stunned the prosecution when he had the killers plead guilty in order to avoid a vengeance-minded jury and place the case before a judge. The trial, then, was actually a long sentencing hearing in which Darrow contended, with the help of expert testimony, that Leopold and Loeb were mentally diseased.
Darrow's closing argument lasted 12 hours. He repeatedly stressed the ages of the "boys" (before the Vietnam War, the age of majority was 21) and noted that "never had there been a case in Chicago where on a plea of guilty a boy under 21 had been sentenced to death." His famous plea was designed to soften the heart of Judge John Caverly, but also to mold public opinion, so that Caverly could follow precedent without too huge an uproar. Darrow succeeded. Caverly sentenced the killers to life plus 99 years. Darrow's closing argument "was something of a popular bestseller, in various editions, during the late 1920s and early 1930s. It was reissued at the time of Darrow's death."
The Leopold and Loeb case raised, in a well-publicized trial, Darrow's lifelong contention that psychological, physical, and environmental influences—not a conscious choice between right and wrong—control human behavior. The public got an education in psychology and medicine and, because Leopold was an admirer, the philosophy of Friedrich Nietzsche.
During the Leopold-Loeb trial, the newspapers claimed that Darrow was presenting a "million dollar defense" for the two wealthy families. Many ordinary Americans were angered at his apparent greed. He had the families issue a statement insisting that there would be no large legal fees and that his fees would be determined by a committee composed of officers from the Chicago Bar Association. After trial, Darrow suggested $200,000 would be reasonable. After lengthy negotiations with the defendants' families, he ended up getting some $70,000 in gross fees, which, after expenses and taxes, netted Darrow $30,000.