Truly beautiful country, and your photos capture that beauty well! Thanks!
As far as English grammar, and speaking as a descriptive linguist, about the only stable words in English are the function words: prepositions, articles, conjunctions, etc. Content words (nouns, verbs, adverbs and adjectives) change easily and often. In fact, one of the great beauties of English is how readily it changes to incorporate new words, technologies and situations. It is a living language and little subject to definitive rules as in Latin, a dead language, which is where the British originally got the idea that grammatical rules had priority over usage. I'm sorry for your irritation, Bill, but I'm afraid "Sierras" is well established in American usage, and its use will continue despite your protest. Just like the use of "impact" as a noun (historically it was a verb) will continue despite my daughter's anger at this common "misuse".