Just because some folks have decided to shame themselves and their city by putting "Sierras" up in lights, it's still not right.

I like to think that this issue was settled many years ago:

       The Spanish word sierra means "range of mountains," and is usually found in combination with other words, such as Sierra Blanca (White Range), Sierra Madre (Mother Range, or Central Range), and Nevada (Snowy Range). Occasionally las sierras is used to designate a group of mountain ranges or ridges. In the Spanish narratives of exploration una sierra nevada is frequently found written without capital initials, referring simply to a snow-covered range of mountains. It was in this that our own Sierra Nevada was first designated. Early in the nineteenth century it was sometimes called the California Range by American explorers, but gradually the Spanish phrase prevailed, and after a while it became a specific name and took its place on all maps. The Sierra Nevada is distinctly a unit, both geographically and topographically, and is well described as "una sierra nevada." Strictly speaking, therefore, we should never say "Sierras," or "High Sierras," or "Sierra Nevadas" in referring to it. Nevertheless, these forms are so frequently found in the very best works of literature and science that it would perhaps be pedantic to deny their admissibility. It becomes, therefore, a matter of preference, and for our part we rather like to keep in mind the unity of our great range by calling it simply "The Sierra" or "The Sierra Nevada."

            Having thus promised not to look askance at "Sierras," we may perhaps be spared the pain of hearing "Sierra Nevada Mountains." Surely one does not say "Loch Katrine Lake," "Rio Grande River," or "Saint San Francisco".

  [This note by Francis Farquhar, the authority on Sierra place names, first appeared in the Bulletin (Sierra Club) in 1928. Largely owing to his editorial effort, the name "Sierras" is even less admissible now than it was then. Some speakers and writers have gone farther than Farquhar would wish: they drop the terminal s all right, but, forgetting the unity of the range, they consider the name to be plural, e.g., "The Sierra are ...." The name "Sierras" is still stuck to by a few recalcitrants who probably concluded that logic has nothing to do with the acceptance place names, and who could cite, in accepted nomenclature, many redundancies such as Little Chico Creek (Little Little Creek).

We cannot argue logically with persons who deprecate logic; nevertheless, we can call them names. So we aver that the man who will say "Sierras" will also say "Frisco," and is probably on a par with the printer who would letter-space lower case type. Such a printer, said Goudy, would steal sheep.]

Excerpt from the 1947 Sierra Club Bulletin.   ed. David Brower

No less an authority than California's own Ansel Adams had this to say:

"The name Sierra is already a plural. To add an s is a linguistic, Californian, and mountaineering sin."

And from a 1944 Sierra Club Bulletin book review of Mountains of the World,  Francis Farquhar ranted:

"But even if all these errors and omissions were corrected, I should have to keep this book from my children, for on nearly half the number of pages it is smeared with the expression "Sierra Nevada Mountains", and any child of mine is bound to know that "sierra" means "mountains" and we don't like double-talk.

The purpose of this review is to plead for greater care in presenting geographical and historical subjects, especially to children."