Amos, the article does not claim that George Washington wrote the vision himself, but that he revealed it to certain of his fellow officers during the harrowing winter of 1777, while commanding his troops at Valley Forge.

Apparently it is found at the Library of Congress, but not being American I'm not sure - is that distinction any indication of credibility?

Here's an article which claims the story is an old hoax, on the grounds that Washington was not a "religious man".

Well, I did check out his Farewell Address (thanks Peter!). If he was not religious, why would he have made such statements as "Of all the dispositions and habits which lead to political prosperity, religion and morality are indispensible supports."

And again, in the last few sentences, "... I fervently beseech the Almighty to avert or mitigate the evils to which they may attend..."

Hmmmm (still) ... daylia