"Its" vs "it's": How and when did the contraction defeat the possessive in the Apostrophe War? For that matter, did standardized grammar emerge at the same time as standardized spelling? Have the rules of modern English grammar been more fluid than spelling?

by chikindiner

I guess my title is unclear. I am aware of when to use 'its' and 'it's'. That's not the question. That's not even a question for this sub.

I am asking about the development of grammar rules, specifically the use of the apostrophe in this case. This site tells me 'it's' was used as possessive regularly in 19th century English.