Manning studied at the Los Angeles County Art Institute, and later, during his US Army service in Japan, drew cartoons for his military base newspaper.

His first notable work was on Brothers of the Spear, a backup feature, created by Gaylord Du Bois, in the Tarzan comic book.

(The adaptation of the sixth, Jungle Tales of Tarzan, also scripted by Du Bois, was drawn by Alberto Giolitti rather than Manning).

Magnus, his and Gold Key's best-known heroic-adventure series, was set in the year 4000, which Manning depicted as clean, airy city scapes populated by shiny robots, handsome men, and beautiful women.

In an era when many science fiction illustrations still showed interstellar spaceships with fins reminiscent of World War II V-2 rockets, Manning offered more exotic craft.

These were collected by Dark Horse Comics as Classic Star Wars: The Early Adventures (ISBN 1-56971-178-X), which omitted the fact that Manning only drew some of the episodes that were written by Steve Gerber and Archie Goodwin.