From left, Tisch family members Wilma, Andrew, Joan, James and Jonathan attend the opening bell at the New York Stock Exchange in 2008. (Mark Lennihan/AP)

Joan Tisch, a billionaire matriarch of the family that co-founded Loews Corp. and co-owns the New York Giants football team, died Nov. 2. She was 90.

The Giants announced her death, but no further details were disclosed.

With a net worth of $4.5 billion, according to the Bloomberg Billionaires Index, Mrs. Tisch was one of the United States’ richest women. The 2005 death of her husband, Robert Tisch, and the 2003 death of his brother and business partner, Laurence Tisch, left her and her sister-in-law, Wilma “Billie” Tisch, overseeing a multibillion-dollar fortune.

Their husbands turned Loews, a theater chain when they bought it in 1959, into a holding company that included hotels, energy companies and insurer CNA Financial Corp. Its principal units today include CNA, Diamond Offshore Drilling, Boardwalk Pipeline Partners and Loews Hotels. In 2008, Loews spun off Lorillard, maker of Newport cigarettes, after owning it for more than 30 years.

Robert Tisch owned half of the Giants football team from 1991 until his death. That share is now owned by their three children — Steve Tisch, a film producer and chairman of the team; Jonathan Tisch, who runs Loews with two cousins, James and Andrew Tisch; and Laurie Tisch, who has helped guide New York cultural institutions including the Center for Arts Education, the Children’s Museum of Manhattan and the Laurie M. Tisch Illumination Fund.

The Tisch family’s large philanthropic footprint in Manhattan includes Tisch Hospital at NYU’s Langone Medical Center, which includes the Joan H. Tisch Center for Women’s Health; Tisch School of the Arts at New York University; and the Tisch Children’s Zoo in Central Park.

Following her husband’s death from a rare form of brain cancer, Joan Tisch donated $10 million to Duke University Medical Center to create the Preston Robert Tisch Brain Tumor Center.

She was a longtime board member at 92nd Street Y in Manhattan, which presents musical and literary events through its Tisch Center for the Arts.

Another of Mrs. Tisch’s long-standing charitable priorities was helping those with AIDS and HIV. She served on the board of the New York-based Gay Men’s Health Crisis and, with her husband, gave $3.5 million to provide the group with office space in Manhattan.

“When Joan Tisch walked through the doors of GMHC in 1986, no one could have predicted the impact she would have on our organization, let alone the influence she would exercise as one of the world’s most visible AIDS advocates and philanthropists,” Marjorie Hill, the group’s chief executive, wrote in 2011.

On her application, according to Hill, Mrs. Tisch wrote: “I have known several people afflicted with AIDS, some of whom have died, and I would like to be of service.”

Joan Hyman was born July 14, 1927, in New York, according to U.S. Census records.

Her father was a Manhattan dentist who helped disabled war veterans attend theater and sporting events. He persuaded Jack Mara, then president of the Giants, to donate 400 seats for each home game to disabled fans and their companions, according to a news release from Loews upon his death in 1981.

Mrs. Tisch received a bachelor’s degree in English in 1948 from the University of Michigan, where she met her husband.