Burlington Northern Class SD9 Number 6170 and SD7 Number 6057 with a boxcar pass a semaphore signal at Fremont, Nebraska on August 20, 1981. Photo by Al Christianson. Number 6170 was built by Electro-Motive Division in September, 1955 as Chicago, Burlington and Quincy Railroad Number 368, Builder Number 20578. It was retired in June, 1986 Number 6057 was built by Electro-Motive Division in December, 1952 as Chicago, Burlington and Quincy Railroad Number 409, Builder Number 17405. It was retired in August, 1983