This stone was placed here in 1908 and is exactly 13 miles from downtown. The Old San Diego road went from downtown Los Angeles (the Pueblo) to (Old Town) San Diego and these stones were placed every mile. It's hard to find information on this but I remember reading somewhere that this was a stagecoach stop. There is another existing stone on Tweedy (mile 12) here in Downey, behind the CVS.
This is also the location of the historic Rives Mansion. It was built in 1912 by James Rives, a prominent newspaperman. It originally sat on a 75 acre lot on which he farmed citrus and walnut trees. This property has recently been restored and looks great. I tried looking for info on tours of the mansion but hit a dead end. If you come and look for this cache, you will be amazed by the mansions granduer.
I've included a spoiler hint to reduce the amount of time hunting because it is a high muggle location.