Billboard's with religious messages or quotes are nothing new, and they aren't only in the south or mid west but right here in Connecticut too. I saw one in Hartford the other day that really hit me, really made me think, and I have done some research on the group that rented the space for this message...
"I am an Atheist, and that is it"- Katherine Hepburn, brought to you by Freedom From Religion ffrf.org
A group of freethinkers who believe in the separation of church and state. Here is the header on their main page.
"The history of Western civilization shows us that most social and moral progress has been brought about by persons free from religion. In modern times the first to speak out for prison reform, for humane treatment of the mentally ill, for abolition of capital punishment, for women's right to vote, for death with dignity for the terminally ill, and for the right to choose contraception, sterilization and abortion have been freethinkers, just as they were the first to call for an end to slavery. The Foundation works as an umbrella for those who are free from religion and are committed to the cherished principle of separation of state and church."
Here is the page for anyone else who wants to check it out: Freedom from Religion