Smith on Washington's Faith:

Gary Scott Smith of Grove City College has a new op-ed on the faith of Washington, which, as expected, is on point.

Although the religious convictions and practices of many presidents have been ignored, Washington’s have been closely scrutinized and endlessly debated. Some authors have portrayed the Virginian as the epitome of piety, and others have depicted him as the patron saint of skepticism. The fact that Washington said almost nothing publicly or privately about the precise nature of his beliefs has evoked competing claims that he was a devout Christian, a Unitarian, a “warm deist,” and a “theistic rationalist.”

One point, however, is not debatable: Washington strongly believed that Providence played a major role in creating and sustaining the United States. In public pronouncements as commander in chief and president, he repeatedly thanked God for directing and protecting Americans in their struggle to obtain independence and create a successful republic.

[...]

Washington firmly believed that God controlled human events. In both his public and private writings, he repeatedly discussed how God providentially helped the United States win its independence against incredible odds, create a unified country out of diverse and competing interests, establish a remarkable constitution, and avoid war with European powers that still had territorial ambitions in North America.

Because God created and actively ruled the universe, Washington insisted, people must revere, worship, and obey him. Although members of his staff wrote most of Washington’s public statements, he oversaw the process, and therefore they expressed what he wanted to convey. Furthermore, Washington routinely used similar language in private letters he wrote.

I've personally done a search for various terms in Washington's archives and you never see Washington use the words "deist," "unitarian," "trinitarian," "the trinity," "holy spirit," "savior" or like terms which would shed light on what he likely specifically believed. Washington only one time ever used the words "Jesus Christ" whose religion he approved a group of Delaware Indians desiring to learn. Washington never uses the word "redeemer"; although his writings reproduce an address from Congress that Washington had delivered to his troops that do. In only one letter does Washington refer to himself as a "Christian," and in more he referred to "Christians" in the third person as though he weren't part of that group. Washington often approvingly mentions "Christianity"; but invariably he seems to equate Christianity and religion with morality itself and stresses the utilitarian effect that such has on society. He never so much suggests that Christianity is the only way to God or that one must become one to be saved.

Accordingly, when Washington approves of Indians converting to Christianity, he explains because it helped to civilize or assimilate them into American society. On two occasions when speaking to Indians who had no desire to convert, Washington referred to God as "the Great Spirit" suggesting their pagan God was the same one he worshipped. Washington may have contradicted himself; however, if one equates Christianity with mere morality and believes all religions are valid ways to God (the test of "sound" religion being that it makes men moral), then Washington's approval of Indians converting to Christianity for utilitarian purposes does not contradict his intimation that the Indians' pagan "Great Spirit" God is the same Providence all religions worship.

Anyway, you can test my claims by searching for these terms yourself.