Daley was born Eleanor Guilfoyle in 1907, in the south side Chicago neighborhood of Canaryville, to a large Irish family.

The youngest son, William M. Daley, served as U.S. secretary of commerce from 1997-2000 and the White House chief of staff from 2011–2012.

In 1972, developers had obtained the city's tentative approval of a proposal to tear down the old Chicago Public Library downtown and replace it with a modern office tower.

Asked her view of the proposal by a Chicago Tribune reporter, Sis Daley observed that she had used the library as a child and said of the demolition, "I don't think that would be nice."

In her later years as a widow, and especially during her son's tenure as mayor, she became something of a matriarch of Chicago; in fact, her birthday of March 4 happens to also be the anniversary of the incorporation of the city.