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This is only a partial answer, coming from my hazy memory of a large research project and some quick online searches. My apologies if it is not acceptable in here and I will quickly bow to any professional historian who cares to comment.
The concept of childhood innocence itself is a product of the Victorian era. Prior and during that era, children were often expected to work in fields and factories, selling matchsticks, or as house girls^1. Children were also considered "sinful" and there is writing from the era speaking of the sexuality / sexual beauty of children. There seems nothing particularly barred one from intercourse with or sexual appreciation for girls under 18.
As far as sexual interaction with pubescent girls, it seems there was significant prostitution of teenage and even pre-teen girls (the age of consent being 12 from 1285 until that era^2 ). Overall the line between child and adult occurred earlier.
As consensual (as it were) sexual interaction with girls 12 and up was accepted if not particularly tasteful, and considering the widespread practice of things such as baby farming^3 , I wouldn't expect too much fuss if an otherwise-respectable man or woman was known to "enjoy the company" of small children. Nothing for polite company, of course, but nothing one would be arrested for.
In the 20th century there were no real protections for children until post-WWII. There were volunteer and non-governmental groups but they often had little authority to act even if something was reported - and much of what they were able to act on was more to do with traditional physical abuse and neglect. It wasn't until the 1960s that child protection services really started to show up in the US. According to this brief by the American Bar Association^5 child abuse became much more visible during that era due to increased recognition by doctors - again, mostly physical abuse and neglect rather than sexual abuse.
Most resources I'm finding online don't differentiate between children age 12-18 and pre-pubescent children, but I would speculate that like so many things, the internet has made child abuse more visible by allowing its adherents to gather and converse easily and (for them) safely. The very bizarre McMartin preschool trial^4 also did much to raise the profile of child sexual abuse, though unfortunately perpetuating the idea of stranger danger rather than the much worse reality of relative and known person abuse.