Originally brought to be used as a source of lumber for rail cross-ties, but they are the wrong species, as the wood does not grow straight grained enough. They are highly invasive, and blight the soil underneath with leaves and seeds that drop. Also, a self pruning tree. At least two people have been killed at the zoo by falling branches. They are planted all around 5 & 805, to the border, and all through the many canyons around el cajon blvd. , university ave. park blvd. and the balboa park areas.
They're also all over the Bay area, and select areas of the Los Angeles region, most notably (that I remember) the Montebello area