Mrs. Daley was 68 and died in her Chicago home surrounded by her husband, former Mayor Richard Daley, and her children, Nora, Patrick and Elizabeth, said Jacquelyn Heard, Daley's former spokeswoman and a family friend.
Maggie Daley had long fought metastatic breast cancer, and she died of complications from that disease, Heard said.
Dr. Steven Rosen, director of the Robert H. Lurie Comprehensive Cancer Center of Northwestern University, said he had seen Mrs. Daley Thursday morning at her home, where in recent weeks she had been under the care of nurses and people from the center's support care program. Rosen said he was called to the home again between 6 and 7 p.m., and arrived about the time of her death.
Rosen, who had cared for Mrs. Daley since 2002, when the cancer had already spread to her lungs, liver and bones, marveled at her resilience.
"She was heroic," he said. "She had great dignity, and she was an inspiration for all of us."
Mayor Rahm Emanuel issued a statement Thursday night praising Mrs. Daley.
"Chicago has lost a warm and gracious first lady who contributed immeasurably to our city," Emanuel said in a statement. "While Mayor Daley served as the head of this city, Maggie was its heart."
Mrs. Daley had been hospitalized several times since her diagnosis, and in recent years had often used a walker, crutches or wheelchair during public appearances. Yet she remained a study in upbeat and gracious perseverance, downplaying her own struggles and eager to cast a spotlight on the needs of others.
As her husband ruled Chicago, Mrs. Daley usually sought to avoid the limelight. But in the background she wielded great influence over her husband, and he in turn used his power to benefit causes she championed — from transforming Meigs Field into a nature park to showering public funds on an after-school charity she founded. When questions were raised about such activities, the former mayor often grew agitated and defensive.
After what Heard described as "a difficult summer" for Mrs. Daley, she attended the Nov. 17 wedding of her daughter Elizabeth "Lally" Daley to Sam Hotchkiss at the upscale Spiaggia restaurant on North Michigan Avenue. The event had been set for New Year's Eve, but was suddenly moved up in apparent deference to Mrs. Daley's failing health. In wedding photos Mrs. Daley was with her family, beaming as always.
The day before Thanksgiving, the former mayor canceled a trip to speak at Harvard and other travel plans. Those close to Mrs. Daley and her husband said the couple had an exceptionally close relationship through their almost 40 years of marriage.
"They thrill at traveling, love movies and often laugh at the same things," TV and film producer Donna La Pietra told the Tribune in 2010. "These are two people who watch over each other, without being cloying or dysfunctionally protective."
Margaret Ann Corbett was born July 21, 1943, the youngest child and only girl among the seven children of Patrick and Elizabeth Corbett of Mount Lebanon, a Pittsburgh suburb where her father owned and operated an auto parts dealership.
She attended St. Francis Academy high school and, after graduating from the University of Dayton, entered a management-training program with Xerox Corp. It was a position that eventually took her to Chicago and a job as a sales representative for Xerox Learning Systems.
She had promised her father she would only spend two years in Chicago before returning to the Pittsburgh area. But at a 1970 Christmas party she met and was smitten by Richard M. Daley, then an attorney and the oldest son of then-Mayor Richard J. Daley, the political boss of Chicago since 1955.
By the following November, the younger Daley and Maggie Corbett had become engaged. They were married in March 1972, in Pennsylvania, and her brother, the Rev. John Corbett, was the celebrant of the Mass. Daley's attendants were his three brothers, Michael, John and William, while his father and mother, Eleanor, sat in the front row of the St. Francis Retreat House.
It was already clear that Richard Daley was being groomed to enter the family business, politics. In 1969, at the age of 27, he was elected as a delegate to a convention that rewrote the Illinois Constitution, and three years later, shortly before the marriage, he declared his candidacy for the state Senate, a post he won and held for eight years until his election as Cook County state's attorney.