This branch was built to serve the citrus packing houses and local construction firms in Orange County. At one point it had two separate crossings, one at Anaheim, and one at Orange, both within about a 12-mile distance.
In the late 19th/early 20th centuries, the Pacific Electric had a line that branched from the Tustin Branch at Santa Ana and ran from to Orange. This line was abandoned during the 1930s, however the northernmost segment remained in place as a "Pacific Electric orphan" for at least another 50 years, to the 1980s. It served a Sunkist packing house in Orange, and connected with the SP Tustin branch at a location called "Marlboro". (As of 2003, the Anaheim crossing at CP College is also a junction where UP trains access BNSF for trackage rights to Santa Ana. The Orange crossing is now the end of the active segment of the branch, at "Marlboro" for the UP and CP "Katella" for the BNSF.) A crossbuck lettered for PE was still in place in the 1980s. Pacific Electric was a subsidiary of SP, but it was separately operated (different train crews). PE was formally merged into SP in 1965.
The remaining track of the Tustin Branch, up to the end-of-line at Tustin, has been removed. The citrus groves were replaced with houses before the track was removed, so much of the right-of-way can still be easily located. The now-abandoned section headed east to Villa Park, then south to El Modena (whose former passenger station is south of La Veta Avenue; El Modena is now a part of Orange) and on to Tustin. The Villa Park-to-Tustin segment was abandoned in 1969 after a bridge washout at Santiago Creek. Part of the route is a maintained public path; the rest is a trail along a utility easement. The Marlboro-to-Villa Park segment was abandoned more recently; much of that section is now a plant nursery.