Just posted some pics I took about 10 years ago of the SP bridge over the Santa Ana river. Enjoy! http://www.trainboard.com/highball/index.php?media/sp-bridge-1.130767/full
The bridge is actually a remnant of the old Pacific Electric railway, that bridge served interurban streetcar lines from Downtown Los Angeles to Santa Ana until 1958.
True, but I always think of the tracks as SP as those were the only things I ever saw run on them. I remember the line only being used occasionally, and that's up in the Garden Grove area. I was too young to ride my bike down to the river crossing, so I don't know how far down they went. Last train I saw in GG was in 1977 (on this line at least), and I think the rails taken out in early 1978.