John Thomas, born in Marshfield, Massachusetts, in 1725, was a successful medical practitioner, entering the British army first as a surgeon, in 1746. He took a prominent part in the French and Indian War, but at its close devoted himself to his profession. He was, however, among the first to counsel resistance to British oppression, and having raised a regiment of volunteers, was appointed brigadier-general by the Provincial Congress on the 9th of February, 1775, and afterward received the same appointment from the Continental Congress on the 22d of June of the same year. On the night of the 4th of March, 1776, with three thousand picked men, he took possession of Dorchester Heights, commanding Boston, where the British were intrenched, and before morning had thrown up a formidable line of earth-works,—an advantage which finally led to the evacuation of the town by the enemy on the 17th of March. The death of Montgomery at the storming of Quebec necessitating the appointment of an experienced officer to command the troops in Canada, this duty was assigned to Thomas,—Congress having advanced him to the rank of major-general on the 6th of March, 1776. He promptly repaired to his new post, but while waiting for promised reinforcements, was attacked by small-pox, from which he died on the 2d of June, 1776, universally respected and deeply deplored.