Barbara, what a great list! I also bookmarked them all.
I have two sources I have used a lot (and couldn’t find the materials elsewhere) but they are not free.
One is the (London) Times Online site, which has all of the issues of the London Times from 1785 to 1985 (scanned) and with a facility to convert stories via OCR though, given what the original fonts look like, it can be sortof silly. But to read the paper is fantastic and it’s great source material if you’re in that era in Britain.
The other is Questia, which also charges a monthly fee also. They have over 77,000 books and a gazillion articles. I’ve found it invaluable and it’s saved me buying books. One can copy and paste text and it even creates references, build your own bookshelf, notes, and so on.