I haven’t done much research, but the only historical records I can find easily deal with the era from 1890 on.
I’m not refuting your claim, just saying that so far I’ve seen people mention these historical documents, but I can’t find them anywhere I’m looking.
Last week, during my evening walk around the neighboorhood, I saw a fellow out by the streetlight, seaching intently for something.
When I asked, he said he'd dropped his car key as he left the house.
"Let me help," I said, "just where were you when you noticed it was gone?"
"Back there about 4 houses.", was the reply.
"Then why don't you look back THAT way?", says I.
He said, "Because the light is better here."
And...Regardless, you won't find anything that supports the LDS contention that 19th century women regularly married in their early teenage years. It was not a commmonplace occurence in society but...it was in the Mormon society (just like the FLDS).
The LDS are unsuccessfully using inaccuracies to distance themselves from the FLDS. In reality, the FLDS, of today, looks, believes and behaves pretty much like the LDS prior to 1890.
When you ask Mormons how their doctrines differ from the FLDS, other than polygamy, you don't get a response. That in itself is telling.