Working primarily as an inker, Sinnott is best known for his long stint on Marvel Comics' Fantastic Four, from 1965 to 1981 (and briefly in the late 1980s), initially over the pencils of Jack Kirby.

"[3] Sinnott's art appeared on two US Postal Service commemorative stamps in 2007, and he continued to ink The Amazing Spider-Man Sunday comic strip until his retirement in 2019.

[5][6] He grew up in a boarding house that catered primarily to schoolteachers, some of whom inspired in the young Sinnott a love of drawing.

[9] Sinnott's first solo professional art job was the backup feature "Trudi"[10][11] in the St. John Publications humor comic Mopsy #12 (Sept.

[13] Sinnott recalled in 1992 "taking the Long Island Rail Road every weekend and working all day Saturday and Sunday.

So I went over to see Stan and he gave me a script right away...."[17] Due to creator credits not generally being given at the time, sources differ on Sinnott's first non-Gill Atlas assignment.

One standard source gives two stories published the same month: the four-page Western filler "The Man Who Wouldn't Die" in Apache Kid #8 (Sept. 1951),[18] and the two-page "Under the Red Flag" in Kent Blake of the Secret Service #3 (Sept.

"[21] The pattern, Sinnott recalled, was for assistant art director Bob Brown to call each in turn to meet with Lee for "maybe ten or fifteen minutes....

[22] During a 1957 economic retrenchment when Atlas let go of most of its staff and freelancers, Sinnott found other work in the six months before the company called him back.

[24] Former EC Comics artist Jack Kamen by this time was the art director of Harwyn Publishing's 12-volume, 1958 Harwyn Picture Encyclopedia for children, and had Sinnott join a roster of contributors that included such notable EC artists as Reed Crandall, Bill Elder, George Evans, Angelo Torres and Wally Wood.

[24] Sinnott also began a long association with publisher George Pflaum's Treasure Chest, a Catholic-oriented comic book distributed in parochial schools.

With Bob Wischmeyer, a Treasure Chest writer-editor, Sinnott collaborated on an unsold college-athlete comic strip Johnny Hawk, All American.

He also began a stint with the low-budget Charlton Comics, teamed as penciler with inker Vince Colletta on several romance-comics stories in series including First Kiss, Just Married, Romantic Secrets, Sweethearts and Teen-Age Love that he would do through 1963.

[20] Sinnott's first collaboration with Jack Kirby, one of comics' most historically groundbreaking and influential creators and the penciler with whom he is most often identified, came with the war-comics story "Doom Under the Deep" in Atlas' Battle #69 (April 1960).

[20][27] Sinnott in 1992 believed his first Kirby collaboration was a Western story titled "Outlaw Man from Fargo",[14] but nothing approximating that appears in standard databases.

Sinnott did one additional Kirby pre-superhero Marvel story, "I Was a Decoy for Pildorr: The Plunderer from Outer Space", in Strange Tales #94 (March 1962), before inking his first Marvel superhero comic: both the cover and the interior of penciler Kirby's The Fantastic Four #5 (July 1962), the issue introducing the long-running supervillain Dr.

[20] But then, in 1965, he returned to Marvel to work virtually exclusively, beginning with his inking the cover and the story, "Where Walks the Juggernaut", of The X-Men #13 (Sept.

[20] After this, Sinnott began his long and celebrated stint on a Marvel flagship title, Fantastic Four, inking Kirby on "The Gentleman's Name Is Gorgon!

Sinnott was a master craftsman, fiercely proud of the effort and meticulous detail he put into his work.

... That slick, stylized layer of India ink that Sinnott painted over Kirby's pencils finished Jack's work in a way that no other inker ever would.

[37]During his years as a Marvel freelancer, and then salaried artist working from home, Sinnott inked virtually every major title, with notable runs on The Avengers, The Defenders and Thor.

[39] The couple had four children: sons Joseph Jr. and Mark, and daughters Kathleen and Linda, the last of whom predeceased Sinnott.

[45] Two Jack Kirby–Joe Sinnott images are among those on the "Marvel Super Heroes" set of commemorative stamps issued by the U.S.