railway horseshoe curve at St Luis Obispo, California

A colorised postcard from about a century ago.

Another colorised postcard although the artist seems not to have bothered with coloring the train.

An Amtrak postcard from 1981 showing the "Coast Starlight"

The trajectory of Southern Pacific's railway (now Union Pacific) north of the town of San Luis Obispo in California, put through in the 1890s, is quite convoluted and includes a horseshoe curve as impressive as the one in Altoona, PA, but it is only single track and less well-known. As well as freight trains, the town is a stop on Amtrak's Coast Starlight and the northern terminus of the Pacific Surfliner.