The original Union Pacific exit from Los Angeles was built by the San Pedro, Los Angeles and Salt Lake railroad, and became part of the Union Pacific system in the 1920s. The well-engineered line has stretches of single track and stretches of two main tracks, with the occasional siding for trains to pass on the single-track sections. The line is operated by Centralized Traffic Control (CTC)
The route is divided into the following subdivisions:
· UP Los Angeles subdivision from Los Angeles (CP East Redondo) to West Riverside Junction
Mileposts are from Los Angeles, with zero being the site of the original station at 4th Street.
The UP Los Angeles line starts at a wye on the east side of the Los Angeles River just north of Washington Boulevard, with one leg of the wye coming from the Ninth Street control point (on the "East Bank Line) and" the other from Redondo Junction, on the line coming across the LA River from the harbor lines. These two legs of the wye cross Soto Street on individual bridges and join at Soto Street Junction (MP 2.1), where the maximum speed is 20 mph. The line is single track, CTC, past a signal bridge, to Downey Road (MP 2.8). Wye tracks heading south east of Downey Road combine into a line southward that crosses the Santa Fe at Hobart Tower and heads to the Los Angeles-Long Beach harbor area. East of the wye, East Yard (MP 4.2), once the sole UP yard in the central Los Angeles area, extends, first six tracks deep, and then two sets of eight tracks deep, along the south side of the main line as far as East Los Angeles (MP 5.9). Along this stretch, the line passes under the Long Beach Freeway (I-710)—in the middle of the yard—and then crosses I-5 and Atlantic Boulevard on bridges at the far east end of the yard, where there is another signal bridge. All along this stretch rail-served lineside industries lie along the north side of the tracks, across from the yard.
Another stretch of single track, CTC, ensues, maximum speed 35 mph, past a spur trailing in on the south side, to Garfield Avenue (MP 7.2), which is also crossed on a bridge. Just east of the Atlantic Avenue bridge, in the vicinity of the East Los Angeles signals, the one time East Los Angeles passenger station still exists on the north side of the line. Eastward from East LA, the line continues through an area of lineside industries and warehouses, many of them no longer (if ever) rail-served. There are signals at Vail Avenue (MP 7.7), detectors at MP 8.3, and grade crossings of Vail Avenue, Maple Avenue (with a spur to industry on the north side of the tracks), Greenwood Avenue, and Montebello Boulevard, with more rail-served lineside industry east of the latter. There are signals atMontebello (MP 8.1), where the speed limit is 65 mph for passenger trains and 50 mph for freights, Bluff Road crosses overhead on a bridge, the line crosses the Rio Hondo on a girder bridge, crosses over Whittier Boulevard on another girder bridge, and then over Paramount Boulevard and Rosemead Boulevard on similar bridges, and passes signals and a 5,918 ft. siding at Pico Rivera (MP 10.5).
Durfee Avenue is crossed at grade. There are more signals at Whittier Jnction (MP 10.8), where the UP Anaheim Branch departs to the southeast, the line curves to the northeast and crosses the San Gabriel River, then joins with a former Southern Pacific branch alongside the San Gabriel River at Bartolo (MP 11.3), where the freight speed limit rises to 60 mph. The line passes under Beverly Boulevard just before reaching the actual junction at Bartolo, but after the tracks have come alongside one another. Passing between a small housing area and I-605, the tracks then pass under the latter, cross Rose Hill Road and Mission Mill Road at grade, pass over Peck Road on a bridge, cross Workman Mill Road at grade, pass under Route 60 and Crossroads Parkway in quick succession and turn east into City of Industry. The line runs along the south side of Walnut Creek for a little way, with the Hacienda Hills to the south. City of Industry, past a small residential area at the west end, is entirely composed of light industry and warehouses, some dating to the 1950s or earlier at the west end, some still under construction towards the east end, nearing Pomona.
The line passes over Seventh Street on a bridge, passes a detector at MP 16.4, signals and a 5,937 ft. siding at City of Industry (MP 16.9), and passes the former UP City of Industry depot (now in use as ??) which lies on the south side of the tracks. The line crosses Turnbull Canyon Avenue at grade and passes over Hacienda Boulevard on a bridge, then crosses Stimson Avenue at grade. At Puente Junction, MP 17.8, a line curves away to the north to head for the former SP City of Industry Yard. This former SP line, in conjunction with the former SP line south from Bartolo, forms the way SP trains reach the SP branches south of Bartolo from their operational base at City of Industry yard. East of Puente Junction, the line crosses Bixby Drive at grade and over Azusa Avenue on a bridge. Continuing between newer warehouses and industries, with three extra tracks on the south side, then one extra track and two separate spurs into warehouses on the south side, and passes another spur south into a warehouse and crosses Fullerton Road, Nogales Street, Fairway Drive, Lemon Avenue and Brea Canyon Road at grade. Immediately east of the latter are signals at Walnut (MP 24.8).
The line passes under Grand Avenue, across State Street on a bridge (inside the Lanterman Development Center), and under Temple Avenue, Route 57 and Route 71. Along this stretch there is an 8,991 ft. siding at Spadra (MP 28.0). In Pomona, the UP line is just a few yards from Southern Pacific’s Sunset Route through that same city, with stations opposite one another. The SP and UP lines simply run alongside each other from Pomona to Montclair (and only a little bit further apart through Ontario). This area is one of much older urban fabric than elsewhere. The lines jointly cross Hamilton Avenue at grade, over White Avenue on a bridge, Park Avenue and Main Street at grade, all west of the stations, pass through the stations (MP 31.9), then over Garey Avenue by a bridge in the middle of the station platforms, Palomares Street at grade at the east end of the station platforms, Towne Avenue and San Antonio Avenue at grade. An SP line crosses the UP at WO Tower (MP 33.0).
The line then crosses Reservoir Street, Ramona Avenue and Monte Vista Avenue at grade, with the ex-SP line to the north sharing the same grade crossing at each location. At Montclair there are six yard tracks to the north of the UP line (but south of the SP track), along with a 5,968 ft. siding on the main line (MP 36.1). There are signals at the west end of Montclair, MP 35.1, Central Avenue crosses the lines and the yard on a bridge, and there are signals at the east end of Montclair, MP 36.7. San Antonio Avenue, Ontario, is crossed at grade (with the UP line and SP line having separate crossings from here on east). Mountain Avenue crosses both lines on a bridge, Vine Avenue crosses at grade, the line crosses over Euclid Avenue on a bridge, past Ontario (MP 37.1). Sultana Avenue is crossed at grade, there is a flat crossing (diamond), 45 mph on the crossing, with a southward spur off the ex-SP line at SP Xing (MP 38.1).
Bon View Avenue is crossed at grade; there are grade crossings at Grove Road, Vineyard Avenue and Archibald Avenue. There are signals at Ballou, MP 40.4, where the maximum speed is 79-60. East of Grove Avenue, where the line turns to head east-southeast, Mission Boulevard runs alongside the tracks to the south for many miles, and Ontario Airport is alongside the tracks to the north between Grove Avenue and Cucamonga Creek (between Vineyard and Archibald Avenues). There is a bridge over Haven Avenue and a grade crossing at Millikan Avenue, with lineside industry on the north side of the tracks. There are two extra tracks on the south side, signals at Champagne, MP 43.3, at the west end of the Mira Loma yard, and a 5,952 ft. siding at Mira Loma (MP 45.2). I-15 passes overhead near the west end of the yard. Route 60 passes overhead at the east end of the yard.
The track crosses over Etiwanda Avenue on a bridge, the line curving southeast crosses over Mission Boulevard to reach the fenced-in autorack yard there, Bellegrave Road, Rutile Road and Jurupa Road are crossed at grade, and the line turns south-southeast. There is a 5,986 ft. siding at Pedley, MP 48.2, and the tracks cross over Limonite Avenue on a bridge. The line now turns away east from Mission Boulevard; Clay Street is crossed at grade, in an area of new light industry and warehouses alongside the tracks. The line crosses the Santa Ana River on a concrete arch bridge, where the heading changes to southeast, past a railroad facility with three tracks on the south side.
There is a wye with a spur to industries on the south side of the track at Arlington (MP 53.2), where the maximum speed rops to 65-55 as the line turns east. The line crosses Jurupa Avenue, Mountain View Avenue and Streeter Avenue at grade. There are signals adjacent to Streeter Avenue grade crossing, a street alongside to the south, Palm Street and Brocton Street are crossed at grade, and then there is a 6,095 ft. siding at Streeter, MP 53.8, where the maximum speed is 50 mph. At this point, the line has turned northeast, and crosses Magnolia Avenue and Riverside Avenue at grade, passes under Pachappa Hill Street which crosses overhead on a bridge, crosses Panorama Road at grade, and passes over Route 91 on a bridge curving to the north. East of the bridge, is West Riverside Junction, MP 56.6, with the BNSF San Bernardino subdivision.
The UP line once kept to the west of the Santa Fe line and east of the 91 freeway, along the line of Vine Street, to its own Riverside depot on the west side of the track north of University Avenue, and joined with the Santa Fe at Riverside junction (MP 58.1). From here over Cajon Pass to Daggett, east of Barstow, UP has trackage rights over the BNSF, originally granted to the Los Angeles & Salt Lake in the early 1900s.