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The Southern Pacific Railroad pushed the line down the San Joaquin Valley in 1874 and began building over the Tehachapi Mountains in 1875. Tunnels were the biggest holdup for construction. The longest of the 18 tunnels on the stretch between Bakersfield and Tehachapi was 1,156 feet and wasn't completed until March 1876. At the same time crews were building northward from Los Angeles. The longest tunnel was 6,966 feet and it wasn't opened until July 1876. The two lines met at Lang in Soledad Canyon in September 1876. The SP then had a line connecting central California with Los Angeles.
In 1915 there were sidings at Gloster, Rosamond, Oban, Lancaster, Denis, Palmdale, Harold, Vincent Berlin, Ravenna, Russ, lang, Humphreys, Honby, and Saugus. Most of these were at least 70 car in length. Berlin siding was renamed Paris during the First World War. Prior to 1927, the Rosamond depot was shut down, the 84 car Fleta and 81 car Ansel sidings were added along with a second siding at Vincent. Prior to 1939, SP added a second siding at Saugus. Prior to 1943 Denis and Oban sidings were lengthened from 50 to 113 cars. In 1942 US&S interlockings were installed in the stations at Vincent and Saugus to speed up operations. Each panel controlled 2 switches and 8 signals. Spring switches lined trains either into the westward or eastward sidings at each installation. During World War II, the train order offices at Rosamond and Ravenna were opened again. In 1943 the sidings at Newhall and Elayon were connected and a switch machine installed at the west switch controlled from the panel in the Saugus depot. This made a siding 173 cars in length which was the longest between Burbank Jct. and Mojave. Also in 1943, tunnel 24 just north of the depot at Saugus was daylighted. Another siding was then added thru the cut with a switch machine at the west end controlled by the operator at Saugus. This new siding was used primarily by eastward trains. Near the end of World War II the SP expanded Mojave Yard to the south and opened a new train order office at East Mojave. The Santa Fe constructed a new alignment so its trains could make use of the longer length of expanded yard. Fleta siding and the wye at Palmdale were removed. After the war the Rosamond train order station was shut down.
After 1946, the railroad began changing the signal system from semaphore
signals to searchlight signals. The SP installed a US&S interlocking panel in
the Mojave depot to control four signals and nine power switches at East Mojave
in 1956. Prior to 1958 the train order station at Palmdale was shut down. Around
1959 the sidings at Gloster and Rosamond plus the wye at Vincent were removed.
The sidings at Ansel, Oban and Denis were lengthened to 171 cars and the train
order station at Ravenna was shut down. I think the signals system was also
changed around this same time period from semaphore to searchlight signals.
During 1960 the siding at Ravenna was lengthened from 88 to 125 cars. Prior to
1966 the siding at Sylmar was lengthened from 104 to 144 cars. In 1967, after
the opening of the Palmdale Cutoff in July, the train order office at Lancaster,
Vincent and Lang were shut down. Palmdale was opened as the new train order
office in the old station and quite a few of the agents at Lancaster were
transfered to Palmdale. The station was equipped with an interlocking panel to
control the junction switch and one switch machine at Denis and one at the new
siding at Palmdale 2. Train crews over the new cutoff were changed at either
Denis or Palmdale 2. Around 1970 a new metal building replace the old station at
Palmdale. After the new yard at West Colton opened in 1973, train crews operated
between the new yard and Bakersfield.
Initially, there were only about ten trains a day operated over the Cut-off. Without block signals, operations over the Cut-off were constricted. The SP finally began installing CTC starting around West Colton in 1979 and worked north. The line from Mojave all the way to the yard at West Colton was under CTC by mid-1980. In 1994 Metrolink built a track just west of the old SP main between Lancaster to just south of the junction of the Palmdale Cutoff then used the original SP line through Saugus to Burbank. Metrolink installed CTC on its Antelope Valley Line in 1997. As reference, I've added a timetable for the Mojave Subdivision. All photographs are on disk 48.