Clark was born in Dallas, Texas on September 23, 1899, to son of Virginia Maxey (née Falls), and William Henry Clark. A graduate of Dallas High School, he served as a Texas National Guard infantryman in 1918; afterward he studied law, receiving his law degree from the University of Texas School of Law in 1922. He was a brother of Delta Tau Delta fraternity, and later served as their international president. He set up a law practice in his home town of Dallas from 1922 to 1937, but left private practice for a period to serve as civil district attorney for the city from 1927 to 1932.

Clark, a Democrat, joined the Justice Department in 1937 as a special assistant to the U.S. attorney general, working in the war risk litigation section. He later moved to the antitrust division, then run by legendary trust-buster Thurman Arnold, and in 1940 was sent to head up the department’s west coast antitrust office. When the Japanese attacked Pearl Harbor the following year, Clark was named by Attorney General Francis Biddle as the Civilian Coordinator of the Alien Enemy Control Program. In this capacity he worked with General John DeWitt, the head of West Coast military forces, as well as his future Supreme Court colleague Earl Warren, who was then attorney general of California, and other top federal and state officials in the lead up to the internment of Japanese Americans. The initial actions involved enforcement of policies to exclude Japanese Americans from areas designated by the military as prohibited, followed by evacuation from “critical zones and areas,” and finally by forcible relocation to prison camps.

Clark was not directly involved with the relocation of Japanese Americans to internment camps, having been reassigned to Washington in May 1942, although he later acknowledged that the government’s relocation program was a mistake  In 1943, Clark was promoted to Assistant Attorney General for Antitrust, and subsequently became the head of the Justice Department’s Criminal Division. Clark also was appointed to head up a new War Frauds unit created to investigate and prosecute corruption by government contractors. During this period he worked closely with, and befriended Harry Truman, whose Truman Committee was investigating war frauds.

One prominent case Clark was involved with during this period included the prosecution of two German spies who came ashore from a German submarine in 1944 to the East Coast of the United States. One, William Colepaugh, was an American citizen, while the other, Erich Gimpel, was a native German. The prosecution took place before a military tribunal on Governor’s Island in New York, only the third such military trial in the nation’s history.

One of President Truman’s first changes in the cabinet that he inherited from Franklin Roosevelt was his appointment of Tom Clark as attorney general in 1945, a switch made in part because of the close personal and professional relationship shared by the two men. Media coverage of Clark’s nomination was generally favorable, and reflected the strength of Clark’s legal and political skills. As a short article in Life Magazine stated, “He is a good prosecutor and good lawyer, but most of all he is a thorough politician.”.

As attorney general, Clark initially continued to focus a good deal of the department’s energy on prosecuting war fraud crimes, as well as aggressively taking on potential antitrust violations. Clark and the White House also challenged John Lewis, the head of the United Mine Workers union, who was threatening a national strike. Acting on Truman’s orders to enforce a law prohibiting strikes against government-run facilities, Clark’s legal battle with Lewis culminated in a Supreme Court case, which he argued successfully, and the Court upheld contempt citations against the union leader.

Early in his tenure as attorney general, Clark initiated a campaign against juvenile delinquency, emphasizing the importance of rehabilitation and education and also implementing procedural changes in federal courts, including the establishment of parole for first federal offenses for juveniles. He convened a national conference at the White House on the topic and created a National Commission on Juvenile Delinquency, selecting a young and inexperienced, but well connected Eunice Kennedy to head it.

Clark played an important role in support of President Truman’s pioneering efforts in civil rights, helping to bring the power of the federal government behind civil rights enforcement. In response to Truman’s anger and disgust over the violent post-war attacks by the Ku Klux Klan on returning black servicemen, Clark began to strengthen the federal government’s response, using increased investigations and, in some cases, an unprecedented filing of federal charges. Clark also initiated an aggressive and groundbreaking legal strategy of filing amicus (friend of the court) legal briefs in federal civil rights cases, which signaled a new and more engaged role for the federal government. The most important of the briefs he filed was in Shelley v. Kraemer (1948), helping to convince the Court to strike down racial covenants in housing contracts restricting the sale of property to blacks. Clark also helped guide the creation of a presidentially established committee on civil rights. The committee released an influential report, “To Secure These Rights” which provided 35 recommendations, including ending segregation, elimination of poll taxes, enactment of a law to protect voting rights, and creation of a civil rights division at the Department of Justice.  The report had an important and lasting influence on civil rights  providing, as Tom Clark later said, “a blueprint of most everything that’s been done in the area of civil rights since that time.”

During his years as attorney general, which coincided with the early years of the Cold War, Clark was responsible for developing and implementing a number of the Truman administration’s aggressive anti-communist policies, including a central feature of Executive Order 9835 concerning the loyalty of federal employees, the Attorney General’s List of Subversive Organizations. This and other policies Clark promoted were often criticized by civil libertarians, though at least some of Clark’s efforts were initiated to deflect congressional criticism of the Truman administration, particularly by the House Committee on Un-American Activities (HUAC). Important early anti-Communist cases during his tenure include the Smith Act, Coplon, and Hiss-Chambers cases.

Clark’s anti-communist efforts also emphasized the promotion of the values of democracy and American citizenship. One way he sought to achieve this was through creation of the Freedom Train, a specially built and privately financed train with railcars designed as a museum and housing more than 100 original documents in U.S. history, including the Bill of Rights, the Emancipation Proclamation, and the Mayflower Compact. The train visited more than 300 cities across the country on its patriotic and educational mission, and during its year of travel was viewed by millions.

After playing an active role in the effort to reelect Truman in 1948, Clark made clear to the White House that he was planning to return to Texas and the practice of law. Following the sudden death of Supreme Court Justice Frank Murphy, however, Truman nominated Clark to fill the vacancy, partly to bolster the majority of Chief Justice Fred Vinson, a former cabinet colleague and friend of Clark who, since his 1946 appointment by Truman, had failed to unify the Court. Numerous attacks from across the political spectrum were leveled at the nomination, including charges of “cronyism,” a lack of judicial experience, and objections based in part on his work at the center of Truman’s anti-communist agenda and, specifically, the Attorney General’s List of Subversive Organizations. Former Roosevelt cabinet members Henry Wallace and Harold Ickes also leveled broadsides, for both personal and ideological reasons. Clark declined to testify at the Judiciary Committee hearing on his nomination, stating that he “didn’t think that a person who had been nominated to the Supreme Court should testify, [since[ it jeopardized his future effectiveness on the Court, [and] that he would invariably testify to something that would plague him.”   He nonetheless was confirmed by the Senate with just eight dissenting votes.

In the four years they served together on the Court, Clark voted with Vinson more than 85 percent of the time, and helped provide him with a reliable majority, however, the Court as a whole remained fragmented. In 1953, Vinson died of a heart attack, and for the remainder of tenure on the Court, Clark served alongside Chief Justice Earl Warren, producing a mix of opinions that makes it difficult to characterize him as either conservative or liberal.

In the area of civil rights, Clark backed decisions supporting government enforcement of laws designed to promote racial equality. To this end he authored or played a key supporting role in a number of the Court’s landmark decisions in this area. Several rulings by the Vinson Court, most notably Sweatt v. Painter and McLaurin v. Oklahoma State Regents (1950), which held that black graduate students must be allowed into “white” state universities and law schools because the separate black school could not provide an education of equal quality, helped lay the groundwork for holdings including Brown v. Board of Education (1954). Clark played a critical behind-the-scenes role in Sweatt and McLaurin that shaped the discussion and provided a workable solution on this issue, helping to “move the Court from considering equality only as a measurable mathematical construct … to what would become known as intangibles.”  Clark’s role as one of two southern justices gave him additional impact in those cases, as well as in Brown and Hernandez v. Texas (1954), in which the Court ruled that excluding persons of Mexican ancestry from juries violated the Constitution, and other decisions. He also authored a number of important decisions on race in the 1960s during the height of the Civil Rights era, including Anderson v. Martin (1964), which held unconstitutional a Louisiana statute because it required the races of those running for office to be printed on a ballot, Burton v. Wilmington Parking Authority, which upheld the concept of state action to find that a private restaurant violated the 14th Amendment’s Equal Protection Clause, and Heart of Atlanta Motel v. United States and Katzenbach v. McClung, which upheld the public accommodations provision of the 1964 Civil Rights Act.

Clark also faced many cases addressing the constitutionality of Cold War era laws and questions of freedom of association involving loyalty oaths and other requirements in which individuals had to affirm that they were not members of particular groups or parties. In this area, Clark generally took a traditionally conservative position in support of such requirements, consistent with his work as attorney general. During his first years on the Court, Clark recused himself from a number of these cases because they had grown out of challenges to policies and laws Clark had helped initiate or implement. In those cases in which he did participate he generally was deferential to the government, and helped provide the Court with a majority affirming the constitutionality of many such laws. Garner v. Board of Public Works (1951) was a 5-4 decision he authored that upheld the right of a city to require its employees to file affidavits that they were not, nor had ever been, members of the Communist Party and to take loyalty oaths to that effect. “Past conduct may well relate to present fitness. Past loyalty may have a reasonable relationship to present and future trust,” he wrote. But Clark also demonstrated a willingness to strike down such laws when they were excessive or overly broad in their application, specifically when they involved the question of whether an individual had knowledge of the organization with which they were allegedly affiliated. Thus, in Wieman v. Updegraff (1952), Clark struck down a loyalty statute from Oklahoma that required all state employees to take an oath that they were not and had never been for the past five years members of any organization that had been on the attorney general’s list of subversive organizations. “Membership may be innocent,” Clark wrote.

Over the next decade, the shifting Court makeup and the evolution of public sentiment, led the Court to find a number of these Cold war statutes unconstitutional. In many instances, Clark was the lone dissenter. Among the most memorable was his solo dissent in Jencks v. United States, in which he labeled the Court’s action a “big mistake,” and suggested that allowing an individual charged with falsely swearing that he was not a member of the Communist Party to see reports made by to FBI witnesses against him, “afforded him a Roman holiday for rummaging through confidential information as well as vital national secrets.” Clark’s dissent sparked congressional legislation overriding the Court’s decision and placing limits on the kinds of documents criminal defendants can request. Even as he would demonstrate more progressive views in other areas of the law, Clark continued to exhibit his belief in the government’s power to prevent people with certain associations from holding certain jobs. Thus, as late as 1967, he dissented in Keyishian v. Board of Regents, in which the Court struck down as unconstitutionally vague a law preventing a state university from hiring “subversives.”

Clark’s background as a former prosecutor and attorney general also influenced his views in the area of criminal procedure and cases involving the rights of criminal defendants, often leading him to support the government’s prosecutorial efforts, particularly during his early years on the bench. In Crooker v. State of California (1958), for instance, he wrote the Court’s 5-4 opinion upholding a murder conviction of a man who was repeatedly refused legal counsel and had not been informed of his right to remain silent during fourteen hours between his arrest and confession because, in Clark’s view, the police tactics were reasonable and the confession voluntary. Six years later, however, he joined with his more liberal brethren in the landmark decision Gideon v. Wainwright (1953) upholding the right to a fair trial and due process under the Sixth Amendment and guaranteeing that an individual defendant must have an attorney appointed for him if he could not afford one. Clark dissented in Miranda v. Arizona, the historic ruling in which the Court held that the Constitution ensures a “right to remain silent,” but he later clarified that he did not disagree with the underlying idea of limits on custodial interrogation. Clark also authored the Court’s landmark decision in Mapp v. Ohio, which broadened the Fourth Amendment’s prohibition on the prosecution’s use of improperly seized evidence, known as the exclusionary rule, to include state prosecutions. Clark’s law enforcement background actually led him to support this approach, because he believed that having a states attorney and a federal prosecutor operating under the same system would ensure that police would be more disciplined and that it would actually lower the risk of evidence being disallowed. Clark demonstrated this progressive understanding right up through his final day on the bench, writing Berger v. New York (1967), an important Fourth Amendment decision in which the Court held unconstitutional a state statute allowing electronic eavesdropping. It was a holding that was quite distant from policies he had imposed as attorney general.

Clark also wrote the decision for the Warren Court in a major religion case involving the First Amendment’s Establishment Clause and reinforcing the principle of separation of church and state. Clark’s opinion in Abington School District v. Schempp (1963), holding that Bible reading exercises and mandated prayer in public schools violated the Constitution, offered the most basic and textual type of constitutional interpretation, “The Constitution says that the government shall take no part in the establishment of religion … No means no,” he wrote.

Clark’s work as a Supreme Court justice generally is viewed favorably by legal historians. As one scholar noted, he was “dedicated to the work of judging, not ideology.”. A leading Supreme Court scholar called Clark “the most underrated Justice in recent Supreme Court history.”  During his career, Clark balanced an underlying judicial restraint with a more expansive, yet principled reading of the Constitution and he demonstrated a rare capacity for change and growth. Justice William O. Douglas, with whom Clark served for all of his time on the Court, commented that Clark had “the indispensable capacity to develop so that with the passage of time he grew in stature and expanded his dimensions.”  Ultimately, Clark came to more fully understand, as he wrote in 1970, that the Constitution “is a living instrument which also must be construed in a manner to meet the practical necessities of the present.”

In the book Plain Speaking by the writer Merle Miller, based on interviews with President Truman, Miller attributes to Truman the statement that appointing Clark to the Court was his “biggest mistake” as President, adding, ”He was no damn good as Attorney General, and on the Supreme Court . . . it doesn’t seem possible, but he’s been even worse.” Allegedly asked by Miller to explain the comment, Miller quotes Truman as stating further: “The main thing is . . . well, it isn’t so much that he’s a bad man. It’s just that he’s such a dumb son of a bitch. He’s about the dumbest man I think I’ve ever run across.”  Truman historians have challenged the accuracy and even the existence of a number of the quotes in the book, including the one about Clark. As one historian who listened to the original interview tapes noted, Miller “changed Truman’s words in countless ways, sometimes thoughtfully adding his own opinions… Worst of all, Miller made up many dates in his book, inventing whole chapters.”  The purported comments also run counter to the warm, personal relationship that Truman and Clark maintained for the rest of their lives. No tape of the interview in which Truman and Miller discussed Clark is known to exist.

Clark assumed senior status, effectively retiring from the Supreme Court, on June 12, 1967. He did so to avoid a conflict of interest when his son, Ramsey Clark, was appointed Attorney General. He was succeeded on the Court by Thurgood Marshall. Lyndon Johnson was said to have appointed Ramsey Clark as Attorney General precisely to force his father off the bench, leaving a vacancy so that Johnson could appoint Marshall as the first African-American Justice on the Supreme Court. After Clark’s retirement, he served as a visiting judge on several U.S. Courts of Appeals, as director of the Federal Judicial Center, and as Chair of the Board of Directors for the American Judicature Society. Clark died in New York City on June 13, 1977, in his son’s apartment home, and was interred in Restland Memorial Park, Dallas, Texas.