Bunker Hill and Breed’s Hill are fortified by Colonial troops.

Learning that the British planned to occupy the high ground in Charlestown, some 1,200 Colonial troops, most commanded by Col. William Prescott, slip into the town. Directed by Lt. Col. Richard Gridley, they first fortify the 115-foot high Bunker Hill, which was out of range of the British guns on ships in the Boston Harbor and on Copp’s Hill, then proceed to fortify nearby 75-foot high Breeds Hill, a half mile closer to Boston and within range of those guns. Although the Colonists attempt to work in silence, Gen. Clinton notices their activity and reports it to Gen. Gage, but Gage does not order an immediate response.