Here is a good article by the science writer Matthew Tontonoz about the history of circumcision in the US, which draws on the book Circumcision by David Gollaher. There was a trend towards circumcision in English-speaking countries during the early 20th century -- it was seen as being cleaner. It also marked higher class status -- if your child was circumcised, that meant he was born in a hospital and delivered by a doctor, rather than at home with a midwife. The circumcision rate went down in Britain, however, because after WWII the NHS decided it would not be covered. Since no similar national health care system has been set up in the US, and it had become something of a cultural norm, doctors continued circumcising newborns.