Mary Pillsbury Lord, 73, an activist in political and humanitarian affairs who succeeded Eleanor Roosevelt as the U. S. representative to the United Nations' Humans Rights Commission in 1953, died of cancer Friday at her home in New York City.

She had been credited with rounding up the women's vote for Dwight D. Eisenhower during his first presidential campaign and he named her to the U.N. post shortly after he took office. She served there until 1961.

At the time of her appointment Mrs. Lord, a New York socialite of prominence, already ahd established a creditable record of achievement in the fields of public health and social welfare, specializing in the problems of children and working mothers.

In addition, she had served in several civil defense in New York City in the early 1940s and in 1943 had been named chairman of the Women's Activities of the National War Fund. This was a federation of voluntary federal relief agencies that placed all recognized war charities under one office.

A year later, Mrs. Lord became national chairman of the Civilian Advisory Committee to aid WAC recruiting. While visiting WAC installations in Europe and the Middle East, she met Gen. Eisenhower for the first time.

Mrs. Lord was elected chairman of the U. S. Committee for the United Nations International Children's Emergency FUnd (UNICEF) in 1948. She toured Europe later that year to inspect homes, schools, hospitals and orphanages in connection with UNICEF's work there.

Her report entitled "Consider These Children," was presented to President Truman at a White House ceremony. It noted that UNICEF had provided food, clothing, and medical care for more than 6 million children.

In early 1952, Mrs. Lord became president of the National Health Council, an organization comprising 42 national voluntary health and welfare organizations. She had served earlier as president of the Council's Committee for the World Health Organization.

She also had worked earlier with Gen. Eisenhower on legislation which made the WACs part of the Army rather than a mere auxiliary unit.

Mrs. Lord became one of the original Eilsenhower campaign leaders in 1952 as cochairman of "Citizens for Eisenhower." She contacted leaders of women's organizations across the country to gain support for the general and flew to a number of states. During these flights she kept busy by recruiting airline hostesses as campaign workers.

After the election, Mrs. Lord met several times with Eisenhower, giving rise to speculation she would be named to an important position in the new administration.

When Mrs. Roosevelt notified him that she was resigning from her U.N. post with the change in administrations, the president-elect announced his intention to name Mrs. Lord to succeed her. He submitted the appointment to Congress after he took office and it was confirmed without opposition.

In addition to serving as American representative on the Human Rights Commission. Mrs. Lord was an alternate delegate and then a delegate to the General Assembly.

During these years, she gained a reputation as a forceful defender of the U.N. conferences around the world, and became a sought-after speaker at luncheons and banquets in this country.

While attending a U.N.-sponsored seminar on the participation of women in public life, held in Addis Ababa, Ethiopia, in 1960, Mrs. Lord was caught in the middle of an attempted coup.

A hole was blown in the wall of her room one night and the hotel became a battleground for a time. She was trapped two days in the crossfire but escaped unscathed.

After leaving the U.N. in 1961, she served on Gov. Nelson A. Rockefeller's Committee on the Education and Employment of Women in New York.

Mrs. Lord also served as a U.S. observer with NATO and as a member of the Atlantic Council during the 1960s.

She became an outspoken supporters of American involvement in Southeast Asia and became one of the founders of Americans for Winning the Peace, a citizens organization formed in 1971 that backed the Nixon Administration's foreign policies.

In 1970 she and her husband. Oswald B. Lord, a partner in the cotton textile firm of Galey & Lord, published a book entitled "Exit Backward Bowing," a collection of anecdotes of their travels in more than 100 countries. Its joint byline read, "by Oswald B. Lord with the advice and dissent of Mary Pillsbury Lord."

Mrs. Lord was born in Minneapolis. Although she was a granddaughter of Charles Alfred Pillsbury who founded the flour company, she once admitted that she was "not the cooking kind of person."

She graduated cum laude from Smith College and was a member of Phi Beta Kappa. It was while attending college that she began her social work. She volunteered to care for children of sick or working mothers.

She returned to Minneapolis and then moved to New York City where she remained active in social work.

"If one's intellectual interest have been stimulated at college, one cannot settle down into an inactive life . . . lying in bed until noon and worrying about nothing but the dinner party that's coming off," she explained.

She served as a voluntary case worker in New York City, as an officer of the East Sied Settlement House, and served as chairman of the Citizen's Health Committee of the New York City Department of Health before World War II.

Mrs. Lord also had been president of the Junior League of New York City Club during this time.

She had served as president of the board of RESCUE, and had served as trustee of Smith College, the American University in Cairo, and was on the visitors committee of both the Fletcher School at Tufts University and Johns Hopkins University's School of Public Health. She had been on the board of directors of Johns Hopkins' School of Advanced International Studies and the Planned Parenthood Association.

Mrs. Lord was a member of a number of clubs, including the Cosmopolitan Club, the National Women's Republican Club, and the Colonial Dames of New York.

She received a citation and official ribbon from Gen. Omar N. Bradley in 1948 for her work in civil defense.

In addition to her husband, of the homes in Stamford, Conn., and New York City, she is survived by two sons, Charles, of Baltimore, and Winston, of New York City, a brother, Phillip Pillsbury, of Minnesota, and five grandchildren.