The MK1200G was the most successful Natural gas powered locomotive to date. Operating from almost 20 years. In 1993 MK Rail began experimenting with Natural gas locomotives as an alternative to regular locomotives. 2 MK1200G's were delivered to UP in 1993, and two to ATSF in 1994. All four of the units stayed in the LA basin for their entire lives. The locomotives used CAT 3612NG prime movers and produced 1200 hp. In 2003 UP returned its two units, these eventually wound up on BNSF. BNSF employed its four MK1200G's on its Los Angeles Junction Railway subsidiary up until May 2012 when they all abruptly returned to their Boise birthplace. Then three sold to a scrap dealer in California, one is still at Boise. The MK's were replaced with Ex-ATSF GP60M's.
Note: MK Rail was bought by Wabtec and renamed Motive Power Industries.
The units held numbers 1200-1203 on BNSF.