[9] In January 1776 artillery captured at Fort Ticonderoga in upstate New York was brought to the Boston area under Henry Knox, providing the Patriot forces with more and larger cannon than they previously had.

The turning point was the capture and fortification of Dorchester Heights on 5 March, allowing the Continental Army to bombard the British fleet in the harbor.

The British evacuated Boston on 17 March under a truce, taking the ships carrying their army to Halifax, Nova Scotia.

[11] In 1778-1780 a force of French Marines from D'Estaing's fleet greatly expanded the fort (probably assisted by Patriot forces), supervised by Chief Engineer du Portail, a French military engineer officer assisting the Continental Army at General Washington's direction.

The newly christened Fort Independence was rebuilt 1801-1803 under the first system of US fortifications and was designed by French-born engineer officer Jean Foncin.

Rearmament of the forts with the new Rodman guns, primarily 15-inch and 10-inch caliber, began during the war, most likely along with some 100-, 200-, and 300-pounder Parrott rifles.

A plaque at the fort states that it was a prototype casemated battery for 15-inch Rodmans, certainly rare in the US and possibly unique.

[19] The Board of Fortifications was convened in 1885 under Secretary of War William Crowninshield Endicott to develop recommendations for a full replacement of existing coast defenses.

[32] Most of the Endicott batteries were years from completion, and it was feared the Spanish fleet would bombard the US east coast.

[33] In 1909 a vast landward defense system was proposed for the Boston area, 70 miles long with its ends at Lynn and Hingham, but none of it was built.

During and after World War I two- and three-gun antiaircraft batteries armed with M1917 3-inch (76 mm) guns on fixed mounts were built at some forts.

Some of these weapons remained in service through early World War II, others were replaced by towed 3-inch guns in the 1930s.

[44] In 1920 a number of weapons deployed in limited quantities, plus the 3-inch gun M1898, were declared obsolete and removed from the forts.

[5][7] The 9th Coast Artillery was the Regular Army component of HD Boston from 1 July 1924 through 23 February 1944, when it was disbanded.

The 241st Coast Artillery was the Massachusetts National Guard component of HD Boston from 30 April 1924 through inactivation on 7 October 1944.

[45][46] This type of weapon was developed in response to the progressive improvement of dreadnought battleships with better guns and armor.

Although the end of World War I meant a general drawdown in US coast defenses, the Boston area was also chosen for one of the first 16-inch (406 mm) gun batteries built by the United States.

The fort had two M1919 16-inch (406 mm) guns on a new high-angle barbette carriage that allowed an elevation of 65 degrees and a range of 49,100 yards (44,900 m).

[48] An alternate proposal in 1920 was to build a naval-type turret with two 16-inch guns on Great Brewster Island, but this was not implemented.

Calf Island Military Reservation was also considered, but the battery was finally built (without a turret) as Fort Duvall.

[49] Early in World War II numerous temporary buildings were again constructed to accommodate the rapid mobilization of men and equipment.

These included heavy earth-covered concrete bunkers for ammunition and fire control, with the guns protected by open-back shields.

[29] Two two-gun 155 mm (6.1 inch) batteries were emplaced in 1942 to quickly provide some defense at key points.

[57] Four 90 mm gun Anti-Motor Torpedo Boat (AMTB) batteries were built in the Boston area.

[29] As new defenses were built, and with little threat to the east coast from enemy air or surface raiders, the heavy weapons at Boston's Endicott-era forts were scrapped in 1942-43.

[29] The removal of most weapons and an Army-wide shift from a regimental to a battalion-based system meant organizational changes in the Boston area.

The former East Point Military Reservation in Nahant is now the Marine Science Center of Northeastern University and is publicly accessible by road.

Fort Dawes was completely demolished to make room for the Deer Island Waste Water Treatment Plant.

The former Fourth Cliff Military Reservation in Scituate is now an Air Force recreation area with some public access; the World War II 6-inch battery and some fire control towers remain.

There are numerous other fire control towers in the Boston area, mostly privately owned, with a few at Cape Ann as well.