research for a future post

I'm looking for someone who knows something about the history of law in the west, particularly law in the United States.

QUESTION: when, if ever, was adultery illegal in the US? If you have an answer, link me to relevant supporting data.

It's for a follow-up on the Gay marriage post I did at TeamPyro, and I could use some research help with that question. If you don't have links but do have appropriately-cited PDFs, e-mail me.