The UP (former SP) still reaches the northern section of Huntington Beach, where a lumber yard near Talbert Avenue still gets rail shipments. This lumber yard is at the southern end of a branch that headed due south from Los Alamitos Junction. Originally the branch continued almost to the shore line, where a Pacific Electric line also ran.
The southernmost three miles likely disappeared in the 1960s, with another mile cut back in the 1980s. The southernmost section was still partly open land into at least the 1970s, although at some point later residential development took over the right-of-way.
Thanks to Mike Palmer for contributing information about this route.