Loretta E. Lynch, a career federal prosecutor, was sworn in Monday, April 27, 2015, as the nation’s 83rd attorney general, as Vice President Joseph R. Biden Jr. told a room full of Justice Department officials: “She is one of you.” Ms. Lynch worked her way up at the Justice Department, starting as a prosecutor and ultimately serving two stints as United States attorney in Brooklyn. Her confirmation last week was the first time in nearly two centuries that a United States attorney was elevated directly to the position of attorney general. The last time was in 1817, when President James Monroe chose William Wirt, the top prosecutor in eastern Virginia, for the job. Her nomination was also a rare instance of President Obama reaching outside his inner circle to fill a crucial post. Unlike Eric H. Holder Jr., whom she succeeded, Ms. Lynch has no personal ties to Mr. Obama or the White House. Ms. Lynch said prosecutors were driven by a desire “to not just represent the law and enforce it, but use it to make real the promise of America, the promise of fairness and equality, of liberty and justice for all.” Later that afternoon, President Obama met with the new Attorney General to welcome her on board and to get an update on several issues — including the current events in Baltimore following the death of Freddie Gray.