1st appearance and origin of Captain Marvel, later renamed Shazam
1st appearance of the Wizard Shazam
1st appearance of Dr. Sivana, a scientific genius and the archenemy of Captain Marvel
1st appearance of Ibis the Invincible and Spy Smasher
1st team appearance of the Seven Deadly Enemies of Man, later renamed the Seven Deadly Sins
While not a precise swipe of Action Comics #1 artwork, this cover and other aspects of Captain Marvel led to DC (formerly National) filing a lawsuit against Fawcett for Captain Marvel too closely resembling Superman
Premiere issue of the series though the copyright notes read issue #2
There exists a scarce Ashcan edition of this issue