Brooke Astor, "New York's First Lady", who spent half a century dispersing her husband's fortune to the city's museums and causes, great and small, has died at the age of 105.

Mrs Astor, who had suffered in recent years from a dementia that all but shrouded her from a vicious family row over her care and fortune, died at Holly Hill, her weekend estate, according to the family lawyer, Kenneth Warner. The cause was pneumonia.

Her death, even in a city awash with art and millionaires, occupied the headlines. "Brooke finds peace at last," said the Daily News. "Heirs set for war," reported the New York Post. "Brooke Astor, Aristocrat of the People", was the title of The New York Times' 3,000-word obituary.

"Today, we are all saddened by the loss of Brooke Astor, a quintessential New Yorker and one of the great philanthropists of our time," said Mayor Michael Bloomberg after her death yesterday.

"Tens of thousands of New Yorkers were the beneficiaries of Mrs Astor’s good will and kind nature, many unaware of the origins of the donations. Her contributions reached a wide variety of causes; The New York Public Library, and the entire city, would not be what they are today without her gracious support.”

Mrs Astor's life changed when she married her third husband, Vincent Astor, the heir to a vast fur and real-estate fortune in 1953, in her early fifties. A secretive man, he curtailed the social life of his wife, who was then a writer for Conde Nast magazines but, on his death in 1959, left her in charge of a $60 million foundation to "for the alleviation of human suffering".

According to Mrs Astor's interpretation, this meant spreading the money across New York, where the Astor family had made its fortune in real estate, receiving letters asking for help and going to see what could be done. She always wore a hat and dressed the same for an Upper East Side lunch as a trip to the Bronx.

“If I go up to Harlem or down to Sixth Street, and I’m not dressed up or I’m not wearing my jewelry, then the people feel I’m talking down to them,” she said, The New York Times recalled. “People expect to see Mrs. Astor, not some dowdy old lady, and I don’t intend to disappoint them.”

Between 1959 and 1997, when the foundation closed, she gave $195 million, supporting causes high and low: from new boilers in youth centres, beachside bungalows, church pipe organs, furniture for homeless families and a charity that took in the pets of the elderly.

But it was to New York's great cultural institutions, the Apollo Theater in Harlem, the Metropolitan Museum of Art, the New York Botanical Garden that she gave her most public gifts. The Bronx Zoo named an elephant after her and after she made the New York Public Library her primary cause, in 1977, its main entrance was named in her honour. In 1996, the city's Landmark Conservancy designated Mrs Astor a living landmark. Two years later, she was awarded the Presidential Medal of Freedom, the nation’s highest civilian honor, for her philanthropy.

“She devoted herself to helping people throughout New York — in all the boroughs,” said David Rockefeller, a family friend. “And she would always visit those to whom she contributed money, and out of respect, she would always arrive well-dressed, with a pretty hat, as if she were calling on the Queen of England.”

Although Mrs Astor receded from public life after her hundredth birthday — marked by a huge gala in 2002 — her name became the subject of breathless headlines last year when her grandson launched an astonishing lawsuit against her 83-year-old son from her first marriage, Anthony Marshall.

Mr Marshall was accused by his son, Philip Marshall, a professor at Roger Williams University in Rhode Island, of looting Mrs Astor's apartment of art, transferring her properties to his name and keeping her in squalid conditions, confined to a sofa smelling of urine and subsisting on oatmeal and peas.

After weeks of press coverage, a settlement was reached without the case coming to court. Mrs Brooke's son admitted no wrongdoing but her friend for 45 years, Annette de la Renta, the wife of Oscar, the fashion designer, was appointed her permanent guardian, along with the bank, JP Morgan Chase & Company. Mrs Brooke was moved from her Manhattan apartment to her estate in Briarcliff Manor, where she died.

Mrs Astor was born Brooke Russell on March 30, 1902, the only child of a career Marine officer who rose to become commandant of the Corps from 1934 to 1936. Her solitary childhood was spent travelling among her father's military postings, from China to the Dominican Republic, Haiti, Hawaii and Panama

When she was 16, she was pushed by her mother into marriage with J. Dryden Kuser, a wealthy Princeton student. The marriage ended in divorce 10 years later. Her second marriage, to Charles Marshall, a stockbroker, was the love of her life, so much so that her son Anthony took Marshall’s name. Marshall died suddenly in 1952 and despite initial reluctance, she married Vincent Astor just a few months later. "After Vincent died I recreated myself," she said during the 1980s. "Now I feel I've become a public monument."

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