Treaty with Tripoli 1796 http://avalon.law.yale.edu/18th_century/bar1796n.asp
The article point 11., of the treaty, is inadequately explained to support the previous poster by jude24 at post 16.
Thanks
Mr. Justice Brewer is the one who wrote for the Court, in the 1892 Holy Trinity Church vs. U.S. case:
[T]he churches and church organizations which abound in every city, town, and hamlet; the multitude of charitable organizations existing everywhere under Christian auspices; the gigantic missionary associations, with general support, and aiming to establish Christian missions in every quarter of the globe.
These and many other matters which might be noticed, add a volume of unofficial declarations to the mass of organic utterances that this is a Christian nation.(Emphasis added.)
So stated the Supreme Court in 1892.