Margaret Eustis Finley, 73, active for many years in civic and cultural affairs in Washington, died Thursday at her home here after apparently suffering a heart attack.

She was the widow of David E. Finley, creator of the National Gallery of Art and its first director, who died here on Feb. 1.

Mrs. Finley had worked closely with her husband in planning and developing the gallery. She had shared all of her husband's artistic interests.

Despite the many demands made on her time in connection with her husband's official duties, Mrs. Finley devoted many hours to volunteer work, particularly with the D.C. chapter of the American Red Cross.

She started volunteering her time to the chapter in 1939, and had been a member of its board of directors since 1941. He name and the Red Cross became practically synonymous through the years.

During World War II, Mrs. Finley headed the District chapter of the Camp and Hospital Service of the American Red Cross.

Her group was in charge of supplementing the needs of soldiers at area camps and posts, including Ft. Belvoir, Bolling Field, Ft. Myer, Ft. Washington and some outlying camps in Virginia.

After the war ended, many volunteers dropped out, but Mrs. Finley continued to devote most of the every weekday to work at her desk at District Red Cross headquarters.

In 1948, while she was serving as chairman of the District Volunteer Services, she explained in an interview why she had decided to stay on.

"After all, the work of caring for the disable from the war has just begun," she said. "There are more hospitalized service men and women in this section than in any other part of the country. And it's the volunteers who are largely responsible for the aid the Red Cross can give them."

Four years later, she was still serving in that position when she became the first woman to receive the "Citizen of the Month" award from the D.C. Department of the American Legion.

She accepted it with her customary modesty, pointing out: "I know this award isn't for me - it's for the Red Cross."

She then noted that the chairman of the volunteer recruitment committee and the chairman of the committee monitoring the services done by volunteers had far more difficult jobs than she.

At that time, Mrs. Finley was overall supervisor of 5,000 volunteers working in nine Red Cross divisions.

Later, in the 1960s, Mrs. Finley was chairman of the D.C. chapter's blood donor recruitment committee. Recently she was one of two recipients of the Mabel Boardman Award, the highest honor given by the D.C. chapter.

Mrs. Finley also had served on the board of directors of the United Gives FUnd and the board of managers of the Washington Home for Incurables.

Born in Washington, she was the daughter of the late Mr. and Mrs. William Corcoran Eustis. One of her grandfathers was Levi P. Morton, vice president under President Benjamin Harrison. Her other grandfather was W.W. Corcoran, founder of the Corcoran Art Gallery.

Mrs. Finley graduated from Foxcroft School in Virginia. She married Mr. Finley in 1931. In 1932, they lived for a year in England where he was honorary counselor of the U.S. Embassy in London.

In addition to her home in Georgetown, she had a country place, Little Oatlands, near Leesburg. It was at one time part of the famous estate, Oatlands, which Mrs. Finley and a sister, Mrs. Eustis Emmet, inherited from their parents.

They donated the manor house and 261 acrs surrounding it in 1966 to the National Trust for Historic Preservation as the memorial to their parents.

Mrs. Finley was an enthusiastic gardener and a member of the Fauquler and Loudoun Garden Clubs of Virginia.

In earlier years, she was talented sculptress. Two of her works are featured in the garden at Little Oatlands, which regularly was opened to the public during Garden Week.

Mrs. Finley had been a member of the Junior League of Washington and belonged to the Sulgrave Club.

In addition to Mrs. Emmet, of Washington, she is survived by two daughters, Renee Beauregrad, of Leesburg, and Mrs. Richard P. Williams of Washington; another sister, Helen Eustis, of Beacon, N.Y., and three grandchildren.

Services will be held at 11 a.m. Monday at St. John's Episcopal Church, Lafayette Square.

The family suggests that expressions of sympathy may by in the form of contributions to the D.C. Chapter of the American Red Cross.