There are only two feasible railroad routes north from the Los Angeles Basin to the Mojave Desert—Soledad Canyon from Saugus to Palmdale and Cajon Pass from San Bernardino to Victorville. Southern Pacific used the Soledad Canyon route for its 1870s entry to Los Angeles from the north. When Santa Fe interests needed a way into the Los Angeles basin from the Barstow area in the 1880s, Cajon Pass was selected, not only because the Soledad Canyon route was already taken, but also because the first line projected south from Barstow was headed for San Diego (as the “California Southern”), not Los Angeles. The lines towards Los Angeles were built later and the original line to San Diego abandoned after several washouts in Temecula Canyon a few years after that. In the late 1960s, Southern Pacific needed a way to bypass traffic congestion on its lines in Los Angeles, and built a line from the Sunset Route at West Colton to the Tehachapi line at Palmdale, over Cajon Pass. This line became known as the “Palmdale Cutoff”.
Cajon Pass exists because the San Andreas earthquake fault runs east-southeast to west-northwest through this area (and is also responsible for the pass through Beaumont and Banning to the east). The fault passes just to the north of San Bernardino (at the base of the San Bernardino Mountains), and the resulting cleft in the mountains (between the San Bernardino Mountains to the east and the San Gabriel Mountains to the west) runs in a northwesterly direction from San Bernardino until it reaches the 3000 ft. level, at which the route to the summit turns north and then east in a vast bowl among mountain peaks in all directions. Cajon Creek runs along the bottom of the northwesterly cleft in the lower regions of the pass. Today, the BNSF (ex-Santa Fe) tracks and the UP (ex-SP) track are joined by Interstate 15 and the various remnants of old US 66 in traversing Cajon Pass.
The former Santa Fe line over Cajon Pass comprises the following subdivision:
On the former Santa Fe, Cajon Pass starts where the former route (until 1994) to Los Angeles via Pasadena and the still current route to Los Angeles via Fullerton come together, just west of the San Bernardino passenger station at milepost 81.4 (from Barstow), 1,040 ft. above sea level. The one-time Santa Fe maintenance shops to the north of the tracks at this point have been replaced by an extensive intermodal yard on both sides of Mount Vernon Avenue (which crosses the tracks on a stylish concrete viaduct). Under the viaduct, an additional track from the Fullerton direction, known as the “short way”, joins from the south, and there is a Metrolink storage yard at this location, south of the tracks, connected with the Metrolink stub-end passenger platforms at the southwest corner of the passenger station area. East of the stub-end platforms is the former Santa Fe depot building, now used by Amtrak. Between the main lines and the depot are additional tracks and platforms used by both Metrolink and Amtrak. There is a total of five Metrolink tracks and two Amtrak tracks in the passenger station. On the BNSF line, there are two main tracks, operated by Centralized Traffic Control (CTC) by a Dispatcher located in the BNSF/UP Joint Los Angeles Dispatching Office in San Bernardino, all the way up the pass from San Bernardino to Summit. (There are, in fact, two main CTC-controlled tracks all the way from Los Angeles to the foot of Abo Canyon, east of Belen, New Mexico, with plans for doubling the line through that bottleneck in the early 21st-century.) In the immediate vicinity of San Bernardino, there are actually three main tracks, all of them CTC-controlled and signaled for bi-directional operations. Track speed at San Bernardino is 30 mph for all trains.
At the east end of the San Bernardino passenger station, following a junction with the currently-disused line to Redlands, the main line makes a sharp turn to the north, passing under a number of street overpasses (5th street, 9th street) and passing through the connections to/from the intermodal yard and crossovers among the main tracks at Seventh Street (MP 80.6), with track speed increasing to 55 mph for freight trains and 60 mph for passenger trains. There are signal bridges containing the necessary signals at both ends of the Seventh Street crossovers. At Baseline, MP 79.9 (adjacent to another street overpass), there are more crossovers and associated signals on bridges (at least at the south (railroad west) end, where the number of main tracks was reduced to two until late 2004. Just north of this point, after passing under the 16th street overpass, the line turns north northwest, and shortly thereafter comes alongside Cajon Boulevard (west of the tracks) and passes under the Highland Avenue street overbridge, a freeway connector overbridge, and then the I-210 overbridge, with track speed increasing to 70 mph for freight trains and 79 mph for passenger trains.
There is a grade crossing at north-south University Avenue, followed by the sidings/spurs on both sides of the track and adjacent steel mill on the east side of the tracks at Ono (MP 76.2, Track 3 only). There is a spur off to the east side, north of the Ono lineside industries. The tracks continue, with an extra track on the east side, straight and even, although on a steady upgrade, across the Palm Avenue grade crossing and through another set of crossovers, at Verdemont (MP 73.9), where the three tracks reduced to two from late 2004 to January 16, 2006, and then a short south-facing spur on the east side just north of Verdemont, before curving around the Cargill grain elevator (to the west of the tracks), where there is a spur into the grain elevator facilities. The latter comprise three tracks with various interconnections among them, with connection to the main line (track 1) at both ends.
North of the grain elevator, the line turns northwest and crosses Cajon Boulevard on a road underbridge, then comes alongside the Colton-Palmdale Cutoff at its Dike siding location. There were intermediate signals at Devore, facing south (railroad west) only, on both tracks (discontinued in late 2004, when the triple track was extended to Verdemont). The speed limit at Devore is 45-40. There is also a spur from track 2, with an eastward facing switch. The three lines (increased from two on January 16, 2006) then continue north northwest side by side, past Intermediate Signals at MP 71.6, across Glen Helen Parkway (formerly Devore Road) on a four track grade crossing at MP 71.0, curve to the left across Cajon Creek and then right again under Interstate 15 (the “Devore Cutoff”) and again head north northwest to the Keenbrook interconnection (from the Colton-Palmdale Cutoff northward to the northbound Santa Fe track 1), with a two-headed signal governing exit from the interconnector, and the Keenbrook crossovers and appropriate signals at MP 69.4 (where three tracks reduced to two from January 16, 2006 until late 2008). North of Devore, track speed for passenger trains increases to 50 mph, while that for freights increases to 45 mph.
At this point, the tracks are on the western edge of the narrowing valley, curving back and forth following the contour of the land. Cajon Creek is in the middle with old route 66 to its east, and Interstate 15 is on the east side of the valley at a higher level than the other road, the creek, and the tracks, which are now climbing more steeply than before. The third track fro, here to Summit was added between 2007 and late 2008, with the additional track being essentially on the west side of the formation. North of Keenbrook, the speed limit drops to 40-35 for the next 10-12 miles.
At Old Keenbrook, where there are Intermediate Signals, the tracks swing left, pass a spur off track 1 at MP 67.3 (a set out track) with a set of intermediate signals on all tracks, cross a dirt road at an unprotected crossing (MP 66.3), and then follow the west side of Cajon Creek around to the east northeast to Blue Cut, MP 65.0, where the tracks, creek, and old Route 66 are very close together. The tracks cross a bridge/culvert over the outlet from Lost Lake before reaching the Blue Cut intermediate signals, and then curve to the north through the Swarthout Canyon Road grade crossing, passing the hot box detectors at MP 64.7 and Intermediate Signals at MP 64.4, and following the hillside (but not the main valley side, which is further west) along the creek to Cajon, MP 62.8, where there is another set of crossovers between the two main tracks and a bridge crossing Cajon Creek.
North of Cajon, there is a spur on the west side of the line Following a set of intermediate signals at MP 62.1 that face east (i.e. affect westbound trains only), the main tracks separate, with track 3 (the original 1880s track) climbing at a ruling gradient of 3% more directly towards the summit, and tracks 1 & 2 (the newest track and the second track, built some 25 years after the original line, with a ruling gradient of only 2.2%) swinging away to the west, curving around to the west southwest, crossing Cajon Creek on a curved bridge in the process, and crossing two dirt roads, before coming directly alongside the Palmdale Cutoff, Canyon siding at the famed Sullivan’s Curve. This location is named after a well-known photographer of the steam era in the 1930s, who took many photographs at this location, before the SP line was built and the Santa Fe curve realigned with a reduced curvature. Beyond Sullivan’s Curve, the track heads northeast for a short distance, then northwest again before passing a set of intermediate signals facing west (affecting eastbound trains) only, curving north to pass under Route 138 (which passes over on a highway overbridge), crossing Cajon Creek again on a girder bridge and passing the Mormon Rocks outcropping. From MP 57 to MP 62, "miles" on Tracks 1 and 2 are 7,370 ft. long, to compensate for the extra distance through Sullivan's Curve
After again curving northwest, the line enters a sweeping curve to the east across a bowl at the upper end of the valley, crosses a dirt road, passes the crossovers and signal bridge(s) at Walker (MP 59.3, named after famed Cajon Pass historian Chard Walker, once an operator at Summit), passes under I-15 on a northeasterly heading, and curves east again to reach Alray (MP 59.0). From trackside at Alray, it is possible to look back down the valley and see trains on the Palmdale Cutoff and Tracks 1 & 2, just south of the route 138 bridges. Here, Tracks 1 & 2 cross over a dirt road (Baldy Mesa Road, formerly US 66) with a girder bridge onto an embankment leading into a cutting that once held the only two tunnels on Cajon Pass, 457.5 ft. tunnel 2 and 380 ft. tunnel 1, both daylighted during the process of adding the third track in 2007-8. The tracks now enter another bowl, east of the first one, which leads all the way to the final approach to Summit,.
There is a set of west-facing (only) intermediate signals at MP 58.x and another set, facing east only, at MP 58.x, with detectors at MP 57.8. At MP 57.2, a concrete bridge crosses another dirt road, and the line then curves around to the south, hugging the edge of the bowl. At Silverwood, MP 56.6, where track speed is 45 mph for all trains, the second interconnection from the Palmdale Cutoff, again arranged for passage of trains to/from the BNSF eastward tracks from/to the southward UP track trails in with appropriate signals on Tracks 1 & 2 and the connector, Track 3 rejoins Tracks 1 & 2, and the tracks curve eastward together to reach the crossovers at the summit of Cajon Pass at MP 55.9 and an altitude of about 3750 ft. (2700 ft. above San Bernardino, approximately 25 track miles away). Track speed at and east of Summit is 55 mph for passenger trains and 50 mph for freights. A small portion of the pre-1972 right-of-way is still visible, even after the addition of the new Track 1.
Meanwhile, Track 3 also crosses Cajon Creek on a bridge with somewhat less curvature than track 1, heads northwest for a short distance alongside and just below I-15, and then heads north northwest until it has passed under Route 138 (which passes over on a highway overbridge separate from that which crosses track 1) before turning directly east, as it again crosses Cajon Creek with a girder bridge adjacent to some intermediate signals. The track passes under I-15 and then across Baldy Mesa Road, heading northeast, passes through the former location of Gish siding in a deep cut heading due east, climbs up past the site of Dell into the broad bowl shared with the north tracks (further up the hillside to the north), past a detector and Intermediate Signals at MP 58.6, and then edges northeast to come alongside track 1 (but at a lower level) by MP 57.2, where the dirt road crosses track 2 at grade. Curving south, track 2 comes alongside track 1 and reaches the same grade as that track before both tracks turn east together to reach Summit.
At Summit, there is a lengthy flat and level area, which includes crossovers, setout tracks to the side, and floodlighting for inspecting westbound trains before they descend the 3% (or even the 2.2%) grade towards San Bernardino, along with fences designed to inhibit access to the tracks by potential vandals, such as those believed to have caused a fatal runaway on track 2 in the 1990s by opening brake cocks not far back in the train. The former road crossing (Summit Truck Trail) just east of the crossovers is now closed off by the security fences. The grade between Summit and Frost is 1.5-1.6%, descending towards Frost.
East of the Summit crossovers, and between the security fences, there are three tracks (the third, having been added during 2004, forming, in effect, a 14,671 ft. siding as far as Martinez) extending around a bend to the northeast in a cutting, and then curving along the hillside on the northwest side of Summit Valley (below the ex-SP line further up the same hillside). A segment of the old (pre-1972) main line across summit (50 feet higher than today’s line) remains as the Martinez Spur on the north side of the tracks. There is a road crossing just east of the Martinez Spur (MP 52.8), and west of the crossovers at the east end of three tracks at Martinez (MP 52.1/2/3/4) that were added with the third track in 2004, a location which also has a dragging equipment detector (MP 52.8). The crossovers are protected by the usual pairs of signals at the ends of the crossover section (“East Bound Control Signals” and “West Bound Control Signals”).
There are more crossovers on the now two main tracks at Lugo (MP 50.1), protected by the usual pairs of signals at the ends of the crossover section, where the line is on the hillside above and to the north of Summit Valley Road, which curves along as the tracks curve back and forth. Following another closed grade crossing, rail line and road turn northeast and continue into Hesperia. There is a detector at MP 48.5, and an airstrip on the east side of the line, after which the road is running alongside on that side of the line again. There are intermediate signals at MP 47.1/2/3/4, Main Street bridges overhead on a concrete bridge at Hesperia (MP 45.1), with more intermediate signals immediately north of the bridge (MP 45.1/2/3/4). There are spurs and an extra track on the east side of the tracks just north of this location, including the Lucerne Valley Subdivision heading off to the east for Cushenbury. A closed concrete underpass once connected two sides of Santa Fe Avenue, the main portion of which is alongside the tracks, now up on an embankment, on the west side. There are more intermediate signals at MP 42.1/2/3/4, before Santa Fe Avenue curves away to the west. Bear Valley Road passes overhead on another modern concrete bridge, after which there is a spur on the west side of the tracks at Thorn (MP 41.1). There are more intermediate signals (MP 40.1/2/3/4) as the line passes to the west of housing built on the east side of the tracks in 2004.
In the days when this line was signaled as double-track, current-of-traffic (Rule 251), the line between San Bernardino and Frost, just ahead, was laid out for left-hand running, so that westbound trains used the easier gradients uphill from San Bernardino. Santa Fe built a “natural crossover” at Frost where the westbound line (the more westerly track on the north side of the bridge) climbed up and over the eastbound line as the tracks curve from northeastward to northward. Once in open country, this is now behind small business and light industry on the west side, with new housing construction on the east side of the line south of the hillock that forms the backdrop to the crossover itself. Fortunately, the line is accessible just north of the still-existing natural crossover, from the Mojave Narrows Regional Park on the east side of the line. Because there is no longer a real need for the “natural crossover”, there is also a set of crossovers, with the usual signals, at Frost (MP 38.0), just at the north end of the ramp up to the crossover bridge. A dirt road crosses the tracks just north of these crossovers.
The Mojave River Narrows themselves are just north of the crossovers at Frost, as the line turns north-northwest, passes under the new concrete and old through-arch road bridges that also cross the river, and enters Victorville. The Victorville Amtrak platform and shelter are on the west side of the tracks (MP 35.7), immediately south of the Sixth Street grade crossing. There is a handthrow crossover just north of the grade crossing, with sidings and helper spurs north of that crossover, on both sides of the line. I-15 crosses over the tracks on the north end of the small yard, while Old Route 66 runs alongside to the west. The large Cemex cement plant and its sidings now occupy the east side of the line, with connections into the easternmost BNSF track at both ends of these sidings. The BNSF East Victorville signals (MP 34.6) are at the north end of the cement plant’s sidings. North of the signals, the tracks cross over the Mojave River (which had been on the east side of the line) on a pair of single track through truss bridges, and turn north-northeast. There are more intermediate signals at MP 32.1/2/3/4, a bridge over a small stream, and some sidings on the east side of the line, as well as one on the west side, just south of the Oro Grande cement plant.
South of that plant, there is a grade crossing at 1st street, up on the embankment next to and east of Old US 66 (here called “National Trails Highway”), and the line crosses over Mill Street on a stone arch bridge. At the Oro Grande cement plant itself, the line angles towards the northeast, while National Trails Highway passes underneath another stone arch bridge in the embankment at the north end of the plant. Just north (“east”) of this point are the crossovers at East Oro Grande (MP 29.4), protected by the usual set of signals. From Oro Grande to Barstow, the line descends at a grade of 0.7%. The highway now moves away from the tracks, further east, as the tracks head across the broad agricultural floodplain of the Mojave River. There are grade crossings over farm roads at Robinson Ranch Road and the south segment of Brymer Road (MP 27.65), intermediate signals at MP 26.1/2/3/4, grade crossings at the north segment of Brymer Road and Turner Road, a bridge in the embankment over Harris Lane, more intermediate signals at MP 23.1/2/3/4, a grade crossing at Darghty Road, a bridge over something unidentified and the grade crossing at Vista Road, Helendale, MP 21.9.
There are industry spurs on the west side of the line, at the end of a parallel side road north of the Vista Road crossing (MP 21.97), and signals at MP 21.1 (Helendale) at the north end of the sours. The line then runs on the east edge of the floodplain, alongside and at the foot of a hillside, on the east side of the line, and at places in short cuttings, temporarily obscuring it from National Trails Highway further to the east. There is a set of intermediate signals along this stretch of line. Northeast of this section, with the line itself now running northeast-southwest, there is a grade crossing at Indian Trail Road, MP 17.3, a dirt road along the west side of the line, a bridge (concrete arch in the embankment) over Holcombe Ranch Road, and intermediate signals at MP 15.1/2/3/4 on the embankment north of the bridge. There is a bridge over something unidentified just south of Hodge, followed by the signals at the south (“west”) end of the crossovers at Hodge (MP 13.6) and the signals at the north (“east”) end of those crossovers.
There are intermediate signals south (“west”) of the Hinkley Road grade crossing (MP 9.1/2/3/4, and a detector at MP 8.5, followed by intermediate signals to its north and then signals at the south (“west”) end of the Lenwood crossovers, MP 6.7, the signals at the east end of Lenwood, and the Lenwood Road grade crossing. There are west-facing signals at MP 5.76, and east facing signals just east of them with a spur going away to the east side of the line, as the line continues to curve to the east-northeast. From Lenwood, there is a road close against the tracks on the northwest side. At Citrine Road, almost into Barstow (at an elevation of 2,105 ft.), the line on an embankment bridges over the road connecting that parallel road back to old US 66. On the embankment at that location, and just further east, are the signals at West R Yard, MP 4.3, immediately followed by the overbridge for the relatively new freeway-style connection west to Route 58, and then the signals at the east end of Valley Junction, MP 3.4. This is the connection between the Cajon Subdivision, from San Bernardino, and the Mojave Subdivision, coming almost due east from South Mojave. Facilitating the entry and exit of trains into and out of the west end of Barstow Yard, and the passage of UP and Amtrak trains that do not enter the yard, the junction here comprises two overlaid wyes, one (the bypass tracks) on the embankment, and one down at ground level (the west connectors into and out of the BNSF Yard), inside the one on the embankment at the north end.