Lois Weisberg has headed the department for more since 1989 and is the only remaining member of Mayor Daley's original cabinet.
Mayor Daley is merging her department with the office of special events to cut costs.
Weisberg says she strongly opposes the decision so she's leaving her job.
Some of her accomplishments include the "Cows on Parade" outdoor art exhibit and events such as the World Music Festival.