FARGO, N.D. (AP) -- Tim Purdon is stepping down as U.S. attorney for North Dakota.
The 46-year-old says he's returning to private practice and will be establishing an office in Bismarck for a national law firm. He would not name the company.
Purdon says his office has made ''tremendous progress'' in the past 4 1/2 years on key priorities, including improving safety on American Indian reservations and tackling crime in the state's oil patch.
President Barack Obama nominated Purdon to the post of U.S. attorney on Feb. 4, 2010. Purdon was confirmed by the Senate on Aug. 5, 2010. He is North Dakota's 18th U.S. attorney.
Purdon's last day is March 12. Assistant federal prosecutor Chris Myers will take over as acting U.S. attorney for North Dakota.