JOHN R. McKERNAN JR. was born in Bangor, Maine. In 1970, he received a bachelor's degree from Dartmouth College, where he was selected to the All-Ivy League Tennis Team. He joined the Army National Guard after graduation and then enrolled in the University of Maine Law School in 1971. While still a student, he was elected to the Maine House of Representatives. He received his law degree in 1974 and was elected to a second term in the Maine legislature, where his colleagues selected him as assistant Republican floor leader. He left the state legislature in 1976 and practiced law at a Portland law firm. He returned to public service and was elected to the U.S. House of Representatives in 1982 and reelected in 1984.