The first woman to lead the Secret Service was sworn in at the White House on Thursday.Veteran agent Julia Pierson now leads the male-dominated agency, which was tarnished last year in a scandal involving agents and prostitutes.US President Barack Obama welcomed Pierson to the role."Obviously, she's breaking the mould in terms of directors of the agencies and I think that people are all extraordinarily proud of her and we have the greatest confidence in the wonderful task that lies ahead and very confident she is going to do a great job," Obama said.Pierson began her career in 1983 as a special agent in Miami. She takes over the top seat from Mark Sullivan who retired in February.