Tom C. Clark, 77, a gregarious, hard-working Texan who served as a justice of the U.S. Supreme Court for 19 years, died in his sleep Sunday in New York at the house of his son, Bamsey Clark.

Justice Clark stepped down from the high court in 1967 to avoid any appearance of conflict of interest when his son was appointed Attorney General by President Johnson. Like his son, Justice Clark also haf been Attorney General.

Since leaving the Supreme Court, to which he was named in 1949 by President Truman, Justice Clark continued to lead an active life, sitting on cases in various U.,S. Circuit Courts of Appeal throughout the country.

He was in New York for an appeals court hearing when he was stricken. The cause of death was not announced immediately.

In a statement describing Justice Clark as "unique in the annals of this Court and the judiciary," Chief Justice Warren E. Burger noted that Tom Clark was the only man ever to sit as a judge in each of the 11 United States judicial ciurcuits.

In addition, Justice Clark also became in 1968 the first director of the federal Judicial Center, which was established to improve the administraion of justice.

Even before leaving the high court, he had begun to travel widely, working with lawyers and judges in behalf of this cause, and both Burger and Attorney General Griffin Bell took note of this yesterday.

"No one in the past 30 years has contributed more to the improvement of justice than Tom Clark," the Chief Justice said. Bell called Justice Clark's endeavors in this area "without equal."

Tall andgenial, with a broad grin frequently breaking out above an ever present bow-tie, Justice Clark was depicted by one writers as "the traveling salesman of justice."

Students of the court described Mr. Clark as generally conservative as a sitting justice when it came to upholding the powrs of the government, particularly in the areas of loyalty and security.

At the same time, he is remembered for his strongly written opinions upholding what is regarded as the liberal position in at least two landmark cases.

Though a former prosecutor himself, Justice Clark was the architect of the 1961 Mapp-versus-Ohio decision, which denied to police in state trials the fruits of illegal searches and seizures.

The Mapp case is one of the most renowned of those by which the Court, under chief Justice Earl Warren, expanded the rights of criminal defendants.

Before the ruling, the Court had interpreted the Fourth Amendment to mean that the federal government could not use in court evidence that was illegally seized.

However prosecutors in many state courts had continued to do so.

Speaking for the Supreme Court majority in the Mapp case, Justice Clark asseted that the due process clause of the 14th Amendment forbade the practice.

Though he might swing toward what is viewed as the liberal viewpoint, Justice Clark did so as a practical man rather than as a visionary.

While some critics of the Warren Court complained that some of its decisions were unrealistic and imposed inordinate restrictions on law-enforcement agencies, Justice Clark did not see things that way in the Mapp case.

"There is no war between the Constitution and common sense," he said.

In that vein, however, Justice Clark did not join in all the celebrated and controversial rulings of the Court on defendants' rights.

A controversial case in which he wrote the opinion for the Court's majority came in 1963, when the Court ruled that Bible-reading exercises in public schools violated Constitutional prohibitions.

The case was known formally as School District of Abington vs Schempp. In his opinion, Clark acknowledged that "we are a religious people whose institutions presuppose a Supreme Being."

But in supporting the decision to prohibit the required readings, he cited the religious freedom that he said is "strongly imbedded in our public and private life."

It was after the court had issued its earlier and even more controversial school prayer ruling that Justice Clark made one of the rare forays by a justice into the public arena.

In a 1962 speech he defended the ruling and took the press to task for what he regarded as failure to report it fully and fairly.

Far from extirpating the last traces of religion in public lift, he said, the Court had merely ruled out ". . . a state-written prayer circulated by a school district to state-employed teachers with instructions to have their pupils recite it in unison at the beginning of each school dap in state-owned buildings."

The Constitution says government shall take no part in the establishment of religion, said Clark, and "No means no. That was all the Court decided."

The son and grandson of men who were lawyers active in Democratic politics, Tom Campbell Clark was born Sept. 23, 1899 in a prosperous section of Dallas. He went to public school there and attended Sunday school faithfully. In 1914 he became an Eagle Scout, one of the first in the nation.

After high school he spent the 1917-18 academic year at the Virginia Military Institute, and then served briefly as an infantry sergeant. Following World War I, he entered the University of Texas, and received his B.A. in 1921 and his law degree the next year.

After joining the law practice of his father and brother, and came to be known as a protege of such legendary political figures as Sen. Tom Connally and former House Speaker Sam Rayburn.

As civil District Attorney of Dallas from 1927 to 1932, Justice Clark is reputed to never lost a case.

Always a modest man, he explained that "A good lawyer doesn't file a suit unless he's sure he'll win."

After a period of private practice in the 1930s, he joined the Justice Department here in 1937.

During service in a variety of Justice Department posts, he won a reputation as a vigorous prosecutor of antitrust cases. He also won praise for his work in the sensitive role of coordinating the work of federal agencies involved in relocating Japanese-Americans on the West Coast during World War II.

In 1945 he was named Attorney General by President Truman, with whom he had worked while Truman was a Senator in charge of an investigaing committee. Justice Clark was said to have been the first man to reach the post of Attorney General by rising through the ranks of the Justice Department.

When Justice Frank Murphy died in 1949 and Justice Clark was named to replace him on the Supreme Court, the appointment was not met with wide-spread enthusiasm. Critics called him unqualified, and contended that his main asset was a history of loyal service to Mr. Truman.

Over the years, however, Justice Clark won increasing respect and recognition as a jurist who had grown in stature while on the bench, and as one who performed valuable functions as ambassador to the bar and to the outside world, and as a conciliator on the court itself.

Perhaps best described as a pragmatist, he could be both forceful anf flexible.

According to one student of the court, if any single term must be used to describe his record on the bench it would be "pro-government."

With prominent exceptions, and within limitations, he upheld police powers anf favored state and federal loyalty programs.

(In one of his last opinions, delivered in January 1967, when he dissented from a majority decision overturning New York loyalty laws aimed at public employees, he wrote that the Court had ". . . by its broadside swept away one of our most precious rights, namely the right of self preservation.")

While he took positions that might be regarded as conservative, he also favored, along with liberals, the vigorous enforcement of antitrust laws.

Of those on the Court when Justice Clark was appointed, only Justice Stanley Reed and William O. Douglas survice.

Douglas, now in precarious health, expressed sympathy to the Clark family and said that if he could not personally attend funeral observances ". . . I will be there in spirit."

Justice Clark lived here for many years in an apartment on Connecticut Avenue in the Kalorama area.

Justice Clark was succeeded on the Court by Thurgood Marshall.

In addition to his wife, Mary, and his son, Ramsey, who was in Europe at the time of his father's death, Justice Clark is survived by a daughter, Mildred Gronlund, of McLean, and seven grandchildren.