On 23 July 1775, Boston selectman Timothy Newell wrote in his diary:
The Castle it is publicly talked will be dismantled. This evening many Guns fired at and from the man of war at N[orth or New, meaning West]. Boston. Ten or twelve transports it is said sailed this day with 150 soldiers upon a secret expedition for provisions.That expedition was very secret indeed—I can’t find any other mention of it. Most likely the rumor Newell had heard was just as unfounded as the plan to dismantle Castle William in Boston harbor, which was, after all, the British military’s strongest protection.
Castle William was never dismantled during the Revolutionary War [ADDENDUM: but see comments]. Eventually that fortification on an island in Boston harbor was replaced by the current structure, completed in 1851. The area is now called Castle Island even though it’s no longer an island. Go figure.
For a sunny view of Castle Island taken from a plane leaving Logan Airport, see Gregory Garretson’s travel journal.