In over 20,000 pages of George Washington's recorded public and private writings and addresses, there is only one recorded mention of the words "Jesus Christ" in an address to Delaware Indians, not written in GW's hand, and in one other address, Washington mentions the person of Christ not by name, but by example. In none of Washington's private letters did he mention Christ by name or by example. Yet, hundreds of times did he use generic titles for God like "Providence." The evidence, therefore, that Washington believed in the "work" of Christ simply is not there. As such, Washington's creed arguably does not merit the label "Christian," but something else.
The one time Washington did mention Christ to Delaware Indians is interesting. The first few times I read this utterance I didn't understand the context. The pietists often present the quotation out of context, suggesting Washington personally tried to convert non-believers to Christ. The reality is, a group of Delaware Indians had already committed themselves to learning "the religion of Jesus Christ" and ways of American life and wished for assistance from Congress. Washington, in an address not written in his hand, point by point restated what the Indians already desired. This was the request Washington received from the Indians:
5th. That the said Delaware Nation have established a Town where numbers of them have embraced Christianity under the Instruction of the Reverend and worthy Mr David Ziesberger whose honest zealous Labours & good Examples have Induced many of them to listen to the Gospel of Jesus Christ, which has been a means of introducing considerable order, Regularity and love of Peace into the Minds of the whole Nation -- the[y] therefore hope Congress will countenance & promote the Mission of this Gentleman, so far away as they may deem expedient; and they may rely that the Delaware Nation will afford every encouragement thereto in their power.
And here is Washington's reply:
Brothers: I am glad you have brought three of the Children of your principal Chiefs to be educated with us. I am sure Congress will open the Arms of love to them, and will look upon them as their own Children, and will have them educated accordingly. This is a great mark of your confidence and of your desire to preserve the friendship between the Two Nations to the end of time, and to become One people with your Brethren of the United States. My ears hear with pleasure the other matters you mention. Congress will be glad to hear them too. You do well to wish to learn our arts and ways of life, and above all, the religion of Jesus Christ. These will make you a greater and happier people than you are. Congress will do every thing they can to assist you in this wise intention; and to tie the knot of friendship and union so fast, that nothing shall ever be able to loose it.
This is the one line the pietists often repeat to try to prove Washington was Christian:
You do well to wish to learn our arts and ways of life, and above all, the religion of Jesus Christ. [My emphasis]
Even reading that one line carefully one sees that Washington was acknowledging that the Indians wished to learn the religion of Jesus Christ, not simply proselytizing out of the blue. Further Washington's explanation to Congress sheds light on the context:
The deputies from the Delaware Nation arrived at Head Quarters two days ago. They presented me with a long memorial on various points, which they intend to present also to Congress. I was a little at a loss what answer to give and could have wished they had made their first application there. But as an answer could not be avoided, I thought it safest to couch it in general but friendly terms and refer them to Congress for a more particular one. Though there is reason to believe, they have not adhered very scrupulously to their pretended friendship, it appeared to me to be our present policy at least to conciliate; and in this spirit my answer was conceived. I hope I may not have deviated from the views of Congress.
Later when addressing Indians who had no desire to convert to Christianity Washington, on two separate occasions, referred to God as "The Great Spirit" exactly as the natives did, suggesting he thought their pagan religion was a valid way to God. At other times, Washington wrote a few letters to evangelizers approving of their efforts to convert the Indians to Christianity and, as he put it, consequently to civilization, expressing a utilitarian concern for the assimilation of Indians and never suggesting that the Indians' pagan religion was "false" or that Christianity was the only way to God.
Washington's approach to religion was that it was useful, even vital for promoting morality that republics need, and as such he was very "religion friendly." Washington was friendly to just about every religion he encountered, including Judaism, Native American spirituality, and orthodox and unorthodox Christian systems. "Sound religion" according to America's key Founders taught a future state of rewards and punishment and produced virtuous people; these Founders did not believe orthodox Trinitarian Christianity was the only way to God, but that most perhaps all world religions were valid. Washington himself clearly believed in an active personal God, but never explicitly professed personal belief in the orthodox Christian system. His God terms were generically theistic (i.e., "Providence") not specifically Christian (i.e., Father, Son, Holy Spirit, Redeemer, etc.). As such Washington is more accurately understood as a "theist" not a "Christian."