United States Attorney
United States Attorneys, aka federal prosecutors or as United States District Attorneys, represent the United States federal government. They do this in U.S. district courts and U.S. courts of appeals. There are 93 U.S. Attorneys in the United States, Puerto Rico, the U.S. Virgin Islands and Guam.
U.S. Attorneys and their offices are a part of United States Department of Justice.
|United States Attorney
|Department of Justice
|President of the United States
Job Description change
Each U.S. Attorney is the boss of their district, and although they are the boss they still can have hundreds of lawyers and staff to help them. All U.S. Attorneys is appointed by the President and is confirmed by the Senate of the United States and they keep their job for 4 years.
Current law says that when there is no U.S. Attorney in a district the Attorney General can appoint one for 120 days.
U.S. Attorney Appointment Controversy change
There was an issue in 2006 where a law was passed which said the Attorney General could appoint a U.S. attorney to serve for as long as needed, which in a way went around the Senate confirmation process.  The issue was fixed with a law passed in 2007. 
The Office of the United States Attorney was created by the Judiciary Act of 1789.