Captain America's first issue was, interestingly, issue #100. Previous titled "Tales of Suspense", it was renamed on April 10th 1968 as "Captain America".
In his first Silver Age appearance, he was joined by Black Panther, who tells him he will maybe take his place in the Avengers. In Avengers #51, he becomes part of the team as Captain America's replacement.
A mint copy of this comic book is now valued at over $1000 - quite a rise from the 12c in cost in 1968! This issue continued the story "This Monster Unmasked", in which Captain America, Black Panther and Agent 13 are trapped in the lair of Franz Guber who is intent on carrying out a plan to cause great damage to the United States!
CAPTAIN AMERICA (1968) #100
Published: April 10, 1968
Penciller: Jack Kirby
Cover Artist: Jack Kirby