This short branch was constructed in 1942, right after the US entered World War II. It connected to Southern Pacific's Coast Line at Goldtree, a few miles north of San Luis Obispo. The line headed west about four miles to Camp San Luis, where California's National Guard is stationed. This branch likely did not see much use after the war, and by the mid 1970s appeared to be out of service.
The tracks remained intact for several decades; however, they were finally removed in the mid 2000s by some local prison labor. (The branch passed by a California state prison.) Many of the rails and other track hardware were donated to the San Luis Obispo Railroad Museum. Museum volunteers used the rails to rebuild an isolated display track next to the museum building (formerly the former SP freight station at San Luis Obispo).
Thanks to Mike Palmer for contributing information about this route.