This statement and its opposite have been dragged and discussed probably to death. But rarely I've heard the people advocating a more secular country mention the Treaty of Tripoli. Sure in the constitution it says something along the lines that the U.S shouldn't favor one religion from another. But that's the point the other side contends, that it's not quite clear that the founding fathers didn't want the U.S. to be a Christian nation, and so on.
 
I know this isn't a super innovative or revolutionary discovery, but to myself this Treaty of Tripoli is more than enough proof to keep (or rather steer) the United States of America as a secular country. 
 
The creationists, they can keep their theories in their church, public schools that want to preach dangerously religious morals should stick to Sunday school. Let's steer clear of things that affiliate us in one way or another to any one religion. 
Although I'm an atheist, I'm not saying that religion should just disappear from the country. Forcing anything of that sort would go against what makes this country what it is. Forcing a religion on the public is also equally wrong.
  
The date of this document is 1797.

Article 11: As the Government of the United States of America is not, in any sense, founded on the Christian religion...