Stevens earned acclaim in 1889 when he explored Marias Pass, Montana, and determined its practicability for a railroad. Stevens was an efficient administrator with remarkable technical skills and imagination. He discovered a pass through the Cascade Mountains that bears his name, set railroad construction standards in the Mesabi Range of northern Minnesota, and supervised construction of the Oregon Trunk Line. Hill promoted him to chief engineer in 1895, and later to general manager. During his time at the Great Northern, Stevens built over a thousand miles of railroad, including the original Cascade Tunnel.