Sounds like a rather impressive souvenir right? Like every good story, however, there is both fact and fiction surrounding this tree.
Let’s dispense with the facts. On June 15, 1775, the Continental Congress in Philadelphia appointed Washington commander-in-chief of the army. Arriving in Cambridge on the afternoon of July 2, Washington met that evening with the New England generals and took command of the army and visited the troops at their lines in Cambridge and Roxbury the following day. (Side note: during the war Washington would travel extensively across the Northeast and Mid-Atlantic states which helped perpetuate the adage "Washington Slept Here" seen across various taverns and inns.) There also was a tree in Cambridge Common which lived approximately 210 years and died in 1923.
J.L. Bell's most excellent Boston 1775 blog notes that by 1837 the descriptions of how Washington took command had been updated to include mention of the large elm tree on the town common, which authors dubbed the "Washington Elm."
The first mention of that tree, according to the Cambridge historian Samuel F. Batchelder and my own best efforts, appeared in an article titled “The Washington Elm” in John Langdon Sibley’s American Magazine of Useful and Entertaining Knowledge in 1837, more than sixty years after the event.
The story gathered more steam with the publication of a fictional journal published during the 1876 festivities of the nation’s centennial year.
By this time there were those questioning the story of the tree and its legend, including Batchelder, who decided
...there would have been no reason for Washington and Artemas Ward, the general he was replacing, to leave their headquarters and stand beneath a tree simply to hand over the order book and conduct a few other formalities. And with the Boston area in peril less than three weeks after Bunker Hill, no one had time for elaborate ceremonies. Washington was much more concerned with inspecting his troops and reconnoitering the enemy, who were rumored to be preparing an attack. (Check-Six.com)
Modern historians tend to dismiss the myth of the Washington Elm though the image of the tree remains a symbol of patriotism in Cambridge, being featured prominently on the city seal. Cambridge celebrates the site with a granite monument (1864) and bronze plaque (1949) alongside cannons and a flag pole in a small park on the western side of the Common. There’s also a plaque embedded into the intersection of Garden and Mason streets that marks the original location of the tree. (Don’t play in traffic.)
Priscilla Bellairs tells us the piece of wood with "a little plaque on it identifying it and proclaiming its significance" was a "much cherished" souvenir from her family:
I really don't know whether it was my mother or father who had initially acquired it; both were strongly patriotic, and had connections to the Boston area in the 1920's, though they didn't meet until about 1932 and married in 1937. I think I became the happy owner when I moved to Cambridge for graduate school at Harvard and my parents thought it was fitting for the elm to return to home ground.
John was fascinated with the oddities that my family tended to preserve, and was happy to display the elm on his desk. However, when we separated, the elm came with me; about six years ago, I gave it as a birthday present to a patriotic and historically-minded friend in the National Guard who was being deployed to Iraq.