John Carroll was born in Upper Marlboro, Maryland, to a merchant father, Daniel Carroll, and a mother, Eleanor Darnall Carroll, descended from Lord Calvert, founder of the colony. He was educated at St. Omer's in France, where he was sent at the age of thirteen. Eventually, after two years of study (1753-1755) at the Jesuit novitiate in nearby Watten and three years of study in Liège, he became a member of the Jesuit order of priests who taught at the school.

Carroll was ordained at Liège in 1767 and renounced all claims to his father's estate in favor of his brothers and sisters. During 1771 he toured Europe as a tutor and kept a sketchy diary of his travels. When Pope Clement XIV suppressed the Society of Jesus in 1773, Carroll obediently left the Continent for England. One year later he returned to his parents' Maryland home...