This abandoned railway was a branch from the Santa Fe's Fullerton-San Diego line. It headed northeast for couple of miles and then turned southeast for a few miles. It served packinghouses at stations called Myford, Browning, Frances, and Kathryn, named (it is believed) for family members of early business owners. The spur also had a separate branch to Tustin.
These lines survived at least as late as the 1960s and the spur lasted until the mid-1980s. At one time it had a girder bridge across the Golden State Freeway (I-5), complete with Santa Fe heralds, but that bridge was removed when the freeway was widened. The section near the junction with the San Diego line is private property and is used as an underground utility corridor. The central portion is completely obliterated with residences. The end of the line, between Frances and Kathryn, can still be traced with a paved path.
Thanks to Mike Palmer for contributing information about this route.