Pauline Phillips, who consoled millions around the world writing the iconic Dear Abby advice column, has died at the age of 94, her syndication service said.
In a statement, Universal Uclick said Phillips - who wrote Dear Abby from 1956 until her daughter Jeanne Phillips took over the column and her alias Abigail Van Buren in 2002 - died on Wednesday in Minneapolis, Minnesota after "a long battle" with Alzheimer's disease.
"I have lost my mother, my mentor and my best friend," Jeanne Phillips said in the statement. "My mother leaves very big high heels to fill with a legacy of compassion, commitment and positive social change. I will honour her memory every day by continuing this legacy."
Long before the internet, the Dear Abby column was a forum for the public discussion of private problems, read by tens of millions of people in hundreds of newspapers around the world.
Phillips, born Pauline Esther Friedman, was the identical twin sister of Esther Pauline Friedman, better known as the equally famous agony aunt Ann Landers. She died in 2000 of cancer.
Their hometown was Sioux Falls, Iowa and - rather aptly for a pair who would be American pop culture icons - their date of birth was July 4, 1918.
While Ann Landers broke into print in Chicago, Dear Abby got her start in San Francisco by pestering the editor of the Chronicle with an offer to write a better advice column than the one the daily had been running.
She was wildly successful. According to Universal Uclick, Dear Abby still appears in about 1,400 newspapers worldwide, has a daily readership of more than 110 million - in print and on its interactive website, dearabby.com  - and receives more than 10,000 letters and e-mails a week. Phillips' daughter, Jeanne, took over the column unofficially in 1987 and officially in 2000.
It is difficult to overstate the column's influence on American culture: in popular parlance, Dear Abby was for decades an affectionate synonym for a trusted, if slightly campy, confidante.
On television, the column has been invoked on shows as diverse as Three's Company, Dexter and Mr Ed. Recording artists The Hearts, John Prine and the Dead Kennedys have released songs titled Dear Abby.
She was known for her wisecracks, a classic example being: "Dear Abby, my wife sleeps in the raw. Then she showers, brushes her teeth and fixes our breakfast - still in the buff. We're newlyweds and there are just the two of us, so I suppose there's really nothing wrong with it. What do you think? - Ed".
"Dear Ed, it's OK with me. But tell her to put on an apron when she's frying bacon."
Agence France-Presse, with additional reporting by The New York Times