Gardner, a political figure in Massachusetts on the eve of the American Revolution, was in the forefront of those urging resistance to the King's dissolution of the General Court in 1774, following the Boston Tea Party.
He was chosen to represent Cambridge in the Middlesex County Convention, called to consider measures for public safety, as well as in the First and Second provincial Congresses.
During the spring of 1775, he was commissioned a Colonel of a regiment he had organized largely at his own expense.
Gardner's rapid rise to prominence ended when he was mortally wounded at the Battle of Bunker Hill, in June 1775.
[2] On the date of his death, July 3, 1775, Gardner was the second-highest ranking American officer killed at Bunker Hill.