He was born in Swords, County Dublin, Ireland, the son of Thomas Montgomery (a member of Parliament) and Mary Franklin Montgomery.
He fought in the British Army in the Seven Years' War). His service was in Canada and the Caribbean. He reached the rank of captain in May 1762. In 1763, when peace was concluded, he went to New York, and in 1765 returned to England.
In England he associated with liberal members of Parliament who supported the colonists in their demands for more freedom.
On April 6, 1772, he sold his Army commission and decided to move back to New York, buying a sixty-seven acre farm at King's Bridge in what is now the Borough of The Bronx of New York City.
On July 24, 1773, he married Janet Livingston, daughter of Robert R. Livingston, a prominent New Yorker who was on the committee that drafted the Declaration of Independence. He then moved to his wife's farm near Rhinebeck, which was to be his home for the few remaining years of his life. In 1775, although having resided in New York only three years, he was elected to the provincial legislature.
He served as the second-ranking brigadier general in the American Revolutionary War, led the army into Canada where he captured two forts and the city of Montreal, and died while attempting to capture the city of Quebec. Shortly afterward, the State of Maryland, when creating a new county, named it Montgomery County in his honor. Subsequently, many other states have also chosen to honor Richard Montgomery by naming counties for him (see below).
The British recognized his body and ordered a decent burial. In 1818, his body was moved to New York City.
Altogether, the following were named for Richard Montgomery: