President Obama appointed veteran U.S. Secret Service official Julia Pierson as the first female director in the agency’s 148-year history Tuesday, nearly a year after a prostitution scandal tarred the reputation of one of the nation’s top law enforcement institutions.

Pierson, 53, who began her career as an agent in Miami three decades ago, has served as chief of staff to the outgoing director, Mark Sullivan, for the past five years. Peers described her as a skilled and dedicated manager who has helped oversee a $250 million project to modernize the institution’s communications and data-management networks.

“Julia is eminently qualified to lead the agency that not only safeguards Americans at major events and secures our financial system, but also protects our leaders and our first families, including my own,” Obama said in a statement.

The appointment does not require Senate confirmation.

Obama’s selection of Pierson comes after an extraordinarily difficult year at the service, which was enveloped by a prostitution scandal exposing its male-dominated culture. She was chosen over former Secret Service official David O’Connor, another top candidate who had interviewed with the president, people familiar with the process said.

Last April, in preparing for Obama’s visit to Cartagena, Colombia, for a summit of Western Hemisphere leaders, several Secret Service agents brought prostitutes to their hotel rooms, where an argument ensued over payment.

In all, 13 male agents and officers were involved in a scandal that highlighted a culture within the service of macho behavior while on the road with the president’s protective detail. Several of the agents, including two supervisors involved in the scandal, were dismissed.

Sullivan implemented new rules governing the use of alcohol and curfew on international trips, along with additional mandatory training for all agents. He announced his resignation last month after apologizing for the scandal.

Pierson “has all the credentials regardless of the events a year ago,” said Barbara Riggs, who served as the agency’s first female deputy director in 2004 and is now retired. “I think that because [the scandal] is still out there in the public’s mind and also in the press, yeah, she will have to deal with what’s remaining from it.”

Sen. Charles E. Grassley ­(R-Iowa) said in a statement Tuesday that the Secret Service had “lost the trust of many Americans and failed to live up to the high expectations placed on it. Ms. Pierson has a lot of work ahead of her to create a culture that respects the important job the agency is tasked with.”

Pierson takes over an agency with a $1.5 billion budget, employing 3,500 agents and 1,400 uniformed officers. The agency provided protection to U.S. dignitaries on more than 5,600 domestic and nearly 400 international trips in 2011, and it operates 142 domestic and 23 international investigative field offices.

In an interview last year, Pierson said the department’s massive technology overhaul, which will take place in the next five years, is critical to enhancing its ability to perform its primary functions: protecting the president and uncovering counterfeiting.

“I don’t think people realize the amount of preparation that goes into a presidential visit, everything from where the president is going to physically arrive, whether by airplane or limousine, to the actual event site,” Pierson said in the interview with the Partnership for Public Service. “We need to know where he’ll walk, where he’ll wait, where he’ll speak from, and all have to be evaluated by the Secret Service to secure his safety.”

Despite Pierson’s long tenure, some agents interviewed about the top contenders for the job told The Washington Post several weeks ago that Pierson was considered a weak candidate among rank-and-file agents because she had spent relatively little time supervising or working high-priority protective details, spending most of her career in administrative jobs.

After graduating from the University of Central Florida with a degree in criminal justice, Pierson joined the Secret Service as an agent in the Miami field office. She served on the protective detail for President George H.W. Bush from 1988 to 1992 before being promoted to management.

Pierson oversaw the Office of Protective Operations, most recently as a deputy director, but with the job of overseeing budgets, resources and personnel assignments. By contrast, O’Connor had protected presidents, the pope and numerous presidential candidates.

“She’s not done her time in the trenches,” said one agent, who was not authorized to speak publicly. “She’s mostly been riding a desk.”

Pierson’s supporters disputed such characterizations.

“That’s totally unfair and inappropriate,” said Ralph Basham, who served as director from 2003 to 2006 under President George W. Bush. “Julie has proven herself to be a leader, as an assistant director and chief of staff. . . . I’d match her up against anyone in the organization.”

Riggs — who oversaw some of Pierson’s earliest assignments on George H.W. Bush’s protective detail — laughed while recalling a presidential trip for a parade in Orlando, where Pierson was sent as part of the advance security team.

Disney’s then-chief executive Michael Eisner and others were delighted to learn that Pierson had once worked as a Disney character in the amusement park, Riggs said.

“They just loved her,” she said.

Carol D. Leonnig contributed to this report.

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