What gets me is letters written by normal people, from the 19th and early 20th century US. Not authors, not statesmen, not business tycoons, not military office

What gets me is letters written by normal people, from the 19th and early 20th century US. Not authors, not statesmen, not business tycoons, not military officers—workers, minor bureaucrats, enlisted soldiers. They tend to read as very "high" language, to modern eyes. Working vocabulary, as you note, seems to be larger as well, even though it's easier than ever to remind oneself of the correct word, with modern tools. > Indeed, it's been my observation that the written register has almost entirely disappeared I think that's a lot of it. Then again, maybe people in the 19th century US spoke like that, too? I haven't looked into it. Surely there's a book about this....