Is this before the whole 'legally rape if it's with a minor' thing came on the books?
No. In United States, the concept has been on the books in one way or another since the 19th century. In fact, the term "jailbait" dates back to the 1930s. As I mentioned in the intro, in the time the story was written, a man could get around it by marrying a girl he wanted to bone. These days, the minimum age of marriage has been synchronized with age of consent in most states, affectively neutralizing this loophole.