IMHO, I would say around the late 50's, early 60's. That"s when we really began to allow liberal thinking into our culture and govt.We started to kick God out of our society and it all began to slide down the slippery slope. If a society kicks God out, it better do so expecting Him to kick back someday.
Dave in WV, Dixie Freedom, and teal325 all made great points so I won't use the space to repeat what they said, just that I agree.

Qtip
Soli Deo Gloria!
To God Alone Be The Glory!