William Daley was born in Chicago, Illinois, in 1948, graduating with a B.A. from Loyola University, Chicago, and an LL.B. from John Marshall Law School.

Except for a period from 1977 to 1980, during which time he sat on the Advisory Council of Economic Opportunity, Daley practiced law privately with the firm Daley and George. He became associated with Amalgamated Bank of Chicago, where he was first vice chairman (1989-1990) and then president and chief operating officer (1990-1993).

Daley returned to the practice of law, becoming a partner with the firm Mayer, Brown & Platt, from 1993 to 1997. In 1993, he served as special counsel to the President on issues relating to the passage of the North American Free Trade Agreement (NAFTA). 

In 1997, Daley became secretary of commerce in the second administration of President William J. Clinton, and he remained at that post until 2000 when he resigned to work on the presidential campaign of Vice President Al Gore.