Despite serving during the
Vietnam War, Cockrum found time to contribute artwork to comics
fanzines such as
Star-Studded Comics and
Fantastic Fanzine. He was then hired as an assistant inker to
Murphy Anderson, Cockrum's work on the feature, beginning with a backup story in
Superboy #184 (April 1972) and recurring in several following issues "established an exciting new vibe". He remained the artist on the
Superboy series after the Legion of Super-Heroes became the main feature of the book with #197 and his art redefined the look of the Legion, creating new costumes and designs that would last until artist
Keith Giffen did a similar revamp in the 1980s. Cockrum is credited with creating team member
Wildfire. Cockrum drew the story wherein the characters
Bouncing Boy and
Duo Damsel were married in
Superboy Starring the Legion of Super-Heroes #200 (Feb. 1974). Cockrum eventually left DC and the
Legion in a dispute involving the return of his original artwork from that issue. Prior to his departure, Cockrum had been preparing to be the regular artist on an ongoing
Captain Marvel Jr. back-up strip in the
Shazam! series for DC. These characters made their debut in
Giant-Size X-Men #1 ([July] 1975), and then in a relaunched
Uncanny X-Men (beginning with issue #94). Cockrum stayed with the title until 1977 (as main penciler on issues #94–105 and 107), when he was succeeded by penciler
John Byrne with issue #108. The final issue of his original, regular run introduced the
Starjammers, a spacefaring superhero team he had originally intended to debut in their own series. He continued to contribute covers for the series until
Uncanny X-Men #126. Cockrum quit his staff job at Marvel in 1979 and his angry resignation letter was printed without his permission in
Iron Man #127 (October 1979) but he continued to work for Marvel as a freelancer. Cockrum was Marvel's primary cover artist during this period, When John Byrne left the
X-Men in 1981, Cockrum returned to the title with issue #145 but left again with issue #164 (Dec. 1982) to work on
The Futurians. a two-part
Starjammers limited series in 1990 and an X-Men short story for
Marvel Holiday Special #1 in 1991. Two unpublished fill-in issues that Cockrum pencilled in the early 1990s for
X-Men and
New Mutants were released together posthumously as the one-shot
X-Men: Odd Men Out in 2008.
The Futurians In 1983, Cockrum produced
The Futurians, first as a
graphic novel (
Marvel Graphic Novel #9), and then as an ongoing series published by
Lodestone Comics. Though it did not last past issue #3, a collected edition was published by
Eternity Comics in 1987 that included the "missing" issue #4. In 1995,
Aardwolf Publishing printed the "missing" issue as
Futurians #0, with a new five-page story by Cockrum and author
Clifford Meth.
Claypool Comics In 1993, Cockrum was recruited by
Claypool Comics to produce work for them, resulting in several stories for Claypool's
Elvira, Mistress of the Dark series beginning with #7. Cockrum was put into rotation on
Peter David's
Soulsearchers and Company, beginning with issue #13, becoming the series' penciler with #17 and penciling most issues through #44, published in 2000. Cockrum contributed a short feature to
Richard Howell's
Deadbeats #18. ==Personal life, illness, and death==