Many Americans like to say that the US was founded as a Christian nation. When was the first significant non-Christian movement?

by Iestwyn

So many people like to take the majority religion of early America as proof that Christianity should remain a dominant cultural force today. Ideally, I'd love to be able to say, "Actually, three quarters of the founding fathers were Muslim," just to completely invalidate their argument. I'll settle for knowing whether there was a decent non-Christian movement around that time.

Thanks in advance!

voyeur324