I have written about this previously, but sometime in 1958 Mort Weisinger and his writers and artists set about creating the character that would come to be known as the Silver Age Superman. It was an era of tremendous creativity, that saw many terrific stories and innovations. Here are some of the most important:
April 1958: Adventure #247 introduces the Legion of Super-Heroes.
July 1958: Action #242 introduces the Silver Age Fortress of Solitude..
September 1958: Action #244 introduces Brainiac and the bottle city of Kandor.
October 1958: Superboy #68 introduces the teen-aged Bizarro.
December 1958: Adventure #255 introduces Red Kryptonite.
February 1959: Superman #127 introduces Titano, the Super-Ape.
April 1959: Jimmy Olsen #37 introduces Lucy Lane.
May 1959: Action #252 introduces Supergirl (Kara Zor-El); Superman #129 introduces Lori Lemaris and Atlantis.
July 1959: Action #254 introduces adult Bizarro.
August 1959: Superman #131 introduces Mr Mxyzptlk (Silver Age version).
April 1960: Adventure #271 introduces the teen-aged Lex Luthor, and establishes the motivation for his hatred of Superboy/Superman.
January 1961: Superboy #86 introduces Pete Ross.
April 1961: Adventure #283 introduces the Phantom Zone.
June 1961: Superboy #89 introduces Mon-El.
(Corrected the intro of the Fortress and Brainiac/Kandor).