In the days leading up to March 17, 1776, Massachusetts was on edge as the British, under General William Howe, prepared to depart Boston. The people had many worries: would Howe burn the city, would he plunder it, would he change his mind and stay? But few if any suspected a British plot to poison Boston.
The British army, holed up and under siege in the city for nearly a year, hemmed in by rebel cannons, had decided to yield its position and flee to Halifax. A tacit agreement had been reached between Howe and American General George Washington, that Boston would not be destroyed so long as the British were allowed to leave unmolested.
But Howe began losing control of his troops. The general had tried to create an orderly process for seizing goods that could be used by the military from the citizens and issuing receipts and certificates for future payment. However, others saw this as a signal that any looting was acceptable.
Soldiers began plundering stores and homes for anything of value they could find. Frustrated, Howe issued a proclamation:
"The commander-in-chief finding, notwithstanding former orders that have been given to forbid plundering, houses have been forced open and robbed, he is therefore under a necessity of declaring to the troops that the first soldier who is caught plundering will be hanged on the spot."
Washington, meanwhile, waited impatiently for the British to depart. Concerned that Howe might be stalling while reinforcements arrived, Washington ordered his troops to continue building fortifications. On March 17, however, the British finally made good on their plans and an armada of ships, loaded with more than 9,000 soldiers and more than 1,000 loyalists fleeing the town, made their way to sea.
Dr. John Warren, whose brother Joseph had perished at Bunker Hill, made an assessment of the town after the British fled.
“The houses I found to be considerably abused inside, where they had been inhabited by the common soldiery, but the external parts of the houses made a tolerable appearance. The streets were clean, and, upon the whole, the town looks much better that I expected. Several hundred houses were pulled down, but these were very old ones.”
The story in Charlestown, which had been burned, was different. Almost nothing was standing, Warren reported, save for an occasional wall or chimney.
Other parts of Boston also bore the marks of the British occupation while under siege.
The British had turned the Old South Church into a riding school for officers. Deacon Hubbard's ornate pew was dragged out and converted to a hog sty. The parsonage was pulled down and burned for fuel, as was the Old North Chapel, dating to 1677, the steeple of the West Church and Boston's celebrated Liberty Tree.
The Common was disfigured and fortified, and Faneuil Hall fitted out as a theater, Warren noted. What cannon the British could not remove with them had been spiked (for the most part) and shells split and shot dumped into the harbor. The Americans would repair and recover much of what had been abandoned.
In total, damage amounted to £323,074. Washington informed John Hancock that his opulent home had been largely unharmed while occupied by British officers, and Abigail Adams wrote to her husband John that their house was "very dirty, but no other damage has been done to it."
But what Warren and fellow physician Dr. Samuel Scott found in the British medical supplies was most shocking. In a workhouse used as a hospital Warren discovered a cache of medicines, some scattered and some in packages, that could be highly useful in treating soldiers or citizens. However, Scott found that upon leaving the British had mixed arsenic into the medicines. He provided an affidavit to the legislature that read:
"I, John Warren, of Cambridge, physician, testify and say, that on or about the twenty-ninth day of March last past, I went into the workhouse of the town of Boston, lately improved as a hospital by the British troops, stationed in said town, and, upon examining into the state of a large quantity of medicine, there by them left, particularly in one room supposed to have been by them used as a medical store-room, I found a great variety of medicinal articles lying upon the floor, some of which were contained and secured in papers, whilst others were scattered upon the floor, loose. Amongst these medicines, I observed small quantities of what, I supposed, was white and yellow arsenic intermixed; and then received information from Dr. Daniel Scott that he had taken up a large quantity of said arsenic from over and amongst the medicine, and had collected it chiefly in large lumps, and secured it in a vessel. Upon receiving this information, I desired him to let me view the arsenic, with which he complied, and I judged it to amount to about the quantity of twelve or fourteen pounds. Being much surprised by this extraordinary intelligence, I more minutely examined the medicines on the floor, and found them to be chiefly capital articles, and those most generally in great demand; and, judging them to be rendered entirely unfit for use, I advised Dr. Scott to let them remain, and by no means meddle with them, as I thought the utmost hazard would attend the using of them. They were accordingly suffered to remain, and no account was taken of them.”
This shocking news reached Massachusetts via the newspapers, and as the horror of the British plot to poison the returning colonists sank in, so did its significance as a propaganda weapon.
The affidavit was quoted and distributed throughout the Colonies and was a useful message to reinforce public antipathy toward the British.
Thanks to History of the Siege of Boston by Richard Frothingham and The Siege of Boston by Allen French