This seems to have happened in the late 1930s or the early 1940s (he says "while I was working on the bomb".) From what I've heard, the US was very conservative at that time; girls & women in general did not have sex before marriage. And additionally was contraception widely available at that time? The sexual revolution happened in the 60s and 70s. So, this does not make any sense. Can someone enlighten me?
Does anyone have any links/references to articles/papers/studies that show that the US was already laissez-faire about sex as early as the late-30s/early-40s?