While reading a recent letter to The Economist, I noticed a citation of the 1997 Treaty with Tripoli on the issue of the US as a religious state. I did a quick Google search to find out more and found a ton of citations around the net from various groups claiming the relevance or insignificance of the document.
The reason this treaty is interesting to people is that it contains the following article (numbered 11):
As the government of the United States of America is not in any sense founded on the Christian Religion,-as it has in itself no character of enmity against the laws, religion or tranquility of Musselmen,-and as the said States never have entered into any war or act of hostility against any Mehomitan nation, it is declared by the parties that no pretext arising from religious opinions shall ever produce an interruption of the harmony existing between the two countries.
Throughout the net, this article is used to bolster the idea that the US is a nation founded on religious freedom and not a theocracy which considers a single religion to be its official religion. Comments are made about this clause being penned by George Washington, when in fact it was translated (or added) by an American diplomat and then ratified by the US Senate and signed by the President.
The Senate ratified the treaty on June 6, 1797 (thanks to the Library of Congress which has the Senate Executive Journal going back to the beginning of time), and it was referred on to the President for his signature.
Contrary to some reports, the President at the time was John Quincy Adams, having been sworn in in Philadelphia on March 4, 1797.
In the end, although it certainly was neither written nor signed by George Washington, it is important to realize that this was a small treaty that was approved by the Senate and signed by the President and thus it is reasonable to state that it represents the interpretation at the time of the ratification, if not the founding of the United States.
However, it's also interesting to look at the context of this treaty. At the time, the US was signing a treaty with Tripoli because they needed to come to an agreement on piracy. The treaty itself contained a payoff to sign the compact and explicitly allowed ships from either nation to carry goods that rightfully belonged to any nation with which the other was at war.
Soon after the treaty's ratification, a new shipping dispute arose and the US and Tripoli "renegotiated" the treaty to a new conclusion in 1805. The renegotiation included a pummeling of the port at Tripoli by the US Navy (such as it was) and ended in an agreement aloowing for the release of 200 US prisoners and other demands for the sum of US$60,000.