Union Pacific's Mojave Subdivision is the former Southern Pacific Palmdale Cutoff, completed in 1967. This is the western edge of San Bernardino, known as Slover on the railroad. On October 9, 2019, UP 4-8-8-4 4014 passes through Slover on its way to West Colton Yard after completing the first run of an operational "Big Boy" over Cajon Pass in history. Surprisingly, in contrast to the large crowds on Cajon Pass, there were only five railfans on the Mill Street overpass to witness this scene!
