Henry P. Merrill, Jr. was born in Portland in 1875. Like his father and his three brothers, Merrill became a physician. He practiced in Portland from 1901 to 1918, when he received a commission as a temporary lieutenant in the naval medical corps. He served in Portland, Bar Harbor, Newport Rhode Island and Philadelphia. He died of natural causes in Brooklyn in 1922, just weeks before he was to ship out to the Asiatic station.