Today, the Massachusetts State Quarter Coin remembers when the Americans took Dorchester Heights and the weather changed the British plan of attack, 242 years ago.
From the Monthly Weather Review of May 1908:
Weather Influences Preceding the Evacuation of Boston, Mass.
By Walter N. Lacy. Dated Harvard University, May 11, 1908.
In a recent study of some climatic influences on American history the writer found reference to the weather conditions which played an important part in the closing history of the siege of Boston.
A careful investigation of all available data on the subject led to the preparation of this paper and of the accompanying maps of the probable weather conditions in the vicinity of Boston for March 4, 5, and 6, 1776.
The maps were drawn from the available data of the local weather conditions at the time and upon present knowledge of the nature, tracks, and velocity of storms in the eastern part of the United States. (See fig. 1.)
Following the battle of Bunker Hill and the arrival of General Washington as Commander-in-Chief in the summer of 1776, the continental forces kept a blockade around the city of Boston all thru the following winter.
As spring advanced Washington resolved upon some effective move, and with the consent of his officers prepared to fortify Dorchester Heights, a position which so commanded Boston and the harbor as to make untenable the British position as long as the Americans occupied those heights.
During the first few days of March, 1776, preparations were hurried for effecting Washington’s plan, and on the nights of Saturday and Sunday, March 2 and 3, cannonading was kept up by the continental forces from Lechmeres Point, Cobble Hill, and Lambs Dam, Roxbury, near the present lead works on Albany street. (See the accompanying sketch map, fig. 2.)
Monday evening, March 4, everything was in readiness and the night was unusually favorable for the execution of Washington’s plan.
Between 7 and 8 o’clock some two thousand men, including a covering party, moved toward Dorchester Heights, under command of General Thomas.
The ground, to a depth of some 18 inches, was frozen so hard that it could not be thrown up as breastworks, and fascines and chandeliers (wooden frames) were carried by the American troops with which to erect their fortifications.
Although the ground was frozen, yet by reason of a southwest wind the night was “remarkably mild,” and the light of the full moon aided the men in their work.
A light haze, or perhaps a radiation fog with the moist southwest wind, combined with the smoke from the cannonading which the Americans had commenced earlier in the evening, settled down over the town and the lowlands and concealed the progress of the work on the heights.
The cannonading of the night, the southwest wind carrying any sound of the American operations out toward the bay, and the smoke and fog kept the British from any suspicion of what Washington’s men were doing, so that when morning broke Howe’s men were much surprised to find what the Americans had accomplished during the night.
Looking through the early morning fog, the fortifications “seemed of indefinite magnitude,” and both General Howe and Admiral Shuldham realized that their positions were insecure as long as the Americans remained on Dorchester Heights.
Consequently General Howe decided to prepare to attack, and about noon between two and three thousand men, under command of General Jones, began to embark in transports.
The plan was for them to drop down in the late afternoon or early evening to Castle Island, whence they could cross to the cove southeast of the American position and attack the Americans from the rear early Wednesday morning.
Tuesday morning had dawned clear and mild, with a bright sun and a warm southerly wind. During the afternoon, however, the storm which had been indicated by preceding fog and winds, and which had probably been advancing up the Ohio Valley, must have reached New York State.
A marked low-pressure area there would have produced strong southeast winds in the vicinity of Boston.
In the afternoon the wind blew furiously, so billowing the harbor that three of the transports were blown upon Governors Island before reaching the Castle.
By night a “rank storm,” as one of the British officers called it, had set in with a fury “such as few remember to have heard,” and the rain fell in torrents, so drenching the Americans who had all day continued to strengthen their position, that one of them wrote in his journal “I never before felt such cold and distress as I did this night, and I believe it was the case in general with our men.”
As morning drew near there was no abatement of the storm, and Wednesday, March 6, commenced amid torrents of rain and a boisterous wind from the southeast.
The center of the storm had probably passed into northern Vermont or New Hampshire, and with the furious southeast gale that was blowing, such a surf beat upon the Dorchester shore where the troops must have landed, that “an attempt to land must have proved fatal.”
Although the rain and the wind continued the greater part of Wednesday with little less fury the time was not being lost by the men under General Thomas.
When the storm and the surf had sufficiently subsided for the British to attack, they realized that the American position was too strong for them, and by night (Wednesday, March 6) the evacuation of Boston had been decided upon.
Eleven days later the city was abandoned, and the entire force under General Howe dropped down in their transports toward Nantasket, sailing thence for Halifax ten days later.
Of the British plan and the results of the storm General Washington wrote Major-General Lee on March 14, as follows:
“A very heavy storm of wind and rain frustrated their design; in my opinion the most fortunate circumstance for them and unfortunate for us that could have happened, as we had everything so well prepared for their reception that I am confident we should have given a very good account of them.”
Whether Washington was right, and whether the British must have evacuated the city had they attacked, will never be known; but it seems certain that the closing chapter of the siege of Boston would have been different had the weather not frustrated General Howe’s plans.
The Massachusetts State Quarter Coin shows with the weather maps of early March 1776 and a map of Dorchester Heights near Boston.