This does not speak to prevalence, mind, but toward the interpretation of child abuse in American history. Not well-versed in the subject, but saw this had no answer.

Beyond the obvious underreporting of child abuse, there were racial and class dynamics that came into play, particularly through gonococcal vulvovaginitis. Gonorrhea functioned as a potential proof of sexual assault in the 19th century. As doctors of the Progressive Era grew more able to ascertain exactly what gonorrhea was, and how it spread, they realized that gonorrhea in little girls was as common in middle and upper-class whites as it was in marginal communities.

Lynn Sacco notes in Unspeakable: Father-Daughter Incest in American History that between 1817 and 1899, more than 900 articles, based on 500 reports, of father-daughter incest appeared in newspapers. Post-Civil War, the reports slowly turned to focus only on marginalized communities (poor whites, "ethnic whites," blacks, etc). But between 1900 and 1940, 136 cases reported, more than half of which occurred during the first decade.

For most of this period, the reports simply vanish. Doctors radically modified their opinions on the etiology of the disease, suggesting non-sexual modes of transmission (sitting on toilet seats methods of contagion) to explain away how it was gonorrhea had spread so unexpectedly among middle and upper-class whites. It was easy enough to explain when it occurred among working-class girls, but the imputation of immortality was taken so seriously that doctors ignored the telltale signs of abuse, even as mothers plead with them.

Finally, the advent of penicillin, the first real treatment, erased the problem, in all senses of the verb: as a cure and as a way of erasing familial sexual assault from the public consciousness.