A Jack Kirby Comic Book Chronology ~ Between The Covers 1941

The Classic Comic Book Blog
Jack KirbyBy 1941 Jack Kirby and Joe Simon were working chiefly for Martin Goodman's Timely Comics. After they created Captain America, they went full time/exclusive for the line. But by year end, they were disillusioned with Goodman, thinking he was cheating them on a share of the profits deal they'd made for Captain America and began making plans to defect to cross town rival DC Comics.
Jack Kirby Portrait by Susan Skaar 1992
Captain Marvel #1
Though Jack and Joe did not do the cover for the iconic CM#1, they did much of the interior artwork.
Captain America #1
Timely/Marvel had already struck pay dirt with the Human Torch & Sub-Mariner, but CA became the flagship, rivaling DC's Superman & Batman
Captain America #2
Notice the new shield. See below for more.
Captain America #3
Surprisingly, this cover wasn't S&K, but rather the equally inimitable Alex Schomburg. We include for the sake of continuity of the early CA.
Captain America #4
Captain America #5 Captain America #6 Captain America #7
Jack gives us a glimpse of the power his work would evoke in the 1960s with this cover in which Cap seems to almost leap out at the reader.
Captain America #8 Captain America #9
Alex Schomburg's busy style was obviously the preferred house look at Timely as S&K seemed to be doing similar layouts. Watch how they change once the team moves to DC in 1942.
  USA Comics #1 Young Allies #1
Bucky and his pals get their own comic. The first of the kid gangs comics that S&K would do to perfection at DC in 1942.
Young Allies #2  
"If momentary exposure to the cosmic rays beyond the Heaviside Layer made a super-man of an ordinary mortal--what fabulous titan of strength and intelligence might the human become who'd spend hours under such forces!"
John L. Chapman from Marvel Stories Vol 2 #2

Marvel Stories Vol 2 #2 1940 Illustrations by Simon & Kirby for the story Cycle that may have inspired Captain America's origin.

MLJ's The Shield from 1940
Notice the chestplate which almost copied exactly as CA's shield in issue one.

Of course, James Montgomery Flagg's iconic Uncle Sam from 1917 have have provided a bit of inspiration as well.

1942 As we've noted, Cap's origin may have been inspired by the writer John Chapman. MLJ Comics also introduced the Shield 14 months before Cap made his first appearance. MLJ threatened Goodman with a lawsuit if they didn't change Cap's shield as it was obviously a duplicate of the Shield's chest plate. Just goes to prove that in the comics, virtually everything is inspired by, evolved from or an outright rip off of something else. The Classic Comic Book Blog