Granny died in 1940,  was cremated & her remains were kept at St Thomas Church in NYC until 1976 when they were moved to the Vanderbilt Mausoleum.

New York, April special wireless.
Mrs. William K. Vanderbilt, widow of a grandson of the founder of the
Vanderbilt dynasty, died today at a hospital in New York, where she had
been a patient since January. She was 76 years old. The funeral will be
held at St. Thomas Church on Tuesday at 2 p m
Although a social leader and a philanthropist on two continents Mrs.
William K. Vanderbilt will be remembered particularly in Paris at this
time for her work in behalf of France and the allies in the world war.
She was one of the leaders in founding the American ambulance at Neuilly
from which emerged the present American Hospital. It was she, with Mrs.
Anne Murray Dike and Miss Anne Morgan, who made possible the Museum of
Franco-American Cooperation at Blerancourt.
During the last war before the United States had entered it Mrs.
Vanderbilt attended wounded at the Neuilly ambulance station and carried
her interest in the allied cause to the United States where she helped
raise funds for works of mercy.
Mrs. Vanderbilt received the class of the Legion of Honor in 1919 in
recognition of her war work, and 12 years later she was made an officer
of the legion.
Her philanthropic donations were numerous and she took an interest in
civic affairs in New York . In 1913 she advocated the employment of
women for police work in New York City and came out against detailing
police in plain clothes to arrest women in the street. Mrs. Vanderbilt
was born Anne Harriman, the daughter of Oliver Harriman, and she was the
wife of Lewis M. Rutherford before her marriage to Mr. Vanderbilt on
April 25, 1903, at St. Mark's, London. The marriage was a union of
members of two great railroad families. Mr. Vanderbilt was 54 years old
at the time and his bride 39. In the small group at the Church were the
then Duchess of Marlborough, now Mrs. Jacques Balsan, who became at
this ceremony Mrs. Vanderbilt's step daughter, the Duke of Marlborough,
Winfield Scott White, a close friend of Mr. Vanderbilt and Henry White,
secretary at the embassy. The colorful International Society of the turn
of the century saw in the marriage the beginning of a social feud. Mr.
Vanderbilt's first wife, born Alva Smith, who became Mrs., Oliver H. P.
Belmont, had established herself as New York's social leader as the
first Mrs. William K. Vanderbilt. Mrs. Belmont opened the feud by
refusing to welcome at Marble House, Newport, anyone who had entertained
Mrs. Vanderbilt. This action, however, did not prevents Mrs. Vanderbilt
from becoming the principal American hostess in France.
Following the war Mrs. Vanderbilt divided her time largely between 1
Sutton Place and with her life long friends, Miss Anne Morgan and Miss
Elizabeth Marbury, and Paris where she maintained a home at 10 rue
Leroux and Europe generally.
Mr. Vanderbilt died in 1920. Two sons were killed in automobile
accidents. When Mrs. Vanderbilt sold 660 Fifth Avenue for $4 million
dollars chroniclers of changing New York took occasion to comment on the
passing of the brownstone mansion era and the end of the "Avenue" as the
home of America's leading families.