American encyclopaedist, editor, and author who was vice president and editor in chief of Encyclopædia Britannica from 1992 to 1997, during its difficult transition from a print product sold door-to-door to an electronic database delivered on the Internet.

McHenry was educated at Northwestern University (B.A., 1966; M.B.A., 1987) and the University of Michigan (M.A, 1967). He joined Encyclopædia Britannica, Inc., in 1967 and two years later went to work for Mortimer J. Adler (Adler, Mortimer J.) at San Francisco Productions. He served as editor of A Documentary History of Conservation in America (1972) and Webster's American Biographies (1974) and in 1975 moved to the Springfield, Massachusetts, offices of G. & C. Merriam Co. (later renamed Merriam-Webster, Inc.). As a senior editor there, he oversaw the publication of several reference works, including Webster's American Military Biographies (1978), Liberty's Women (1980), and Webster's New Biographical Dictionary (1983).

Returning to Britannica in 1982, McHenry served as editor of the Compton's Yearbook (the annual supplement to Compton's Encyclopedia), joined the editorial staff of the Encyclopædia Britannica, and was named director of Britannica yearbooks (which then numbered five). In 1986 he became managing editor of Encyclopædia Britannica, in 1990 general editor, and in 1992 editor in chief. In addition to heading the editorial transition to CD-ROM-based reference works, including Britannica CD (1994), he served as a key architect of Britannica Online, the first Internet-based encyclopaedia, released in 1994.

McHenry's interest in information theory and critical thinking led to his Internet publication of How to Know (1998).