For some reason, Americans (U.S. ones) have always found the french dirtier than them. What was considered dirty is of course tame more than ninety years later. This was under-the-counter stuff you wouldn't want to be seen in public with, translated from foreign publications that weren't named. I don't have the exact date, but it was before Harold Ross's edict that cartoons only having one or no captions became the standard.
