Short answers, pulled from the story.
DC Comics was founded in February 1935 under the name National Allied Publications by entrepreneur Major Malcolm Wheeler-Nicholson. The company later became known as Detective Comics, Inc. after a partnership formed in 1937 with Harry Donenfeld and Jack S. Liebowitz.
Action Comics #1 released in June 1938 and introduced Superman, the first superhero character archetype, created by Jerry Siegel and Joe Shuster. The issue also featured Lois Lane and the office boy who became Jimmy Olsen.
The Silver Age of Comic Books began in October 1956 when editor Julius Schwartz created a new Flash named Barry Allen in Showcase #4. This era also saw the formation of the Justice League of America and the introduction of characters like Supergirl and Brainiac.
The 1985 publication of Crisis on Infinite Earths by Marv Wolfman and George Pérez realigned the DC Universe timeline into pre- and post-Crisis eras. This 12-issue limited series featured key character deaths and simplified continuity discrepancies.
DC Comics became a subsidiary of Time Warner in 1989 when Warner Communications merged with Time Inc. The merger of AT&T's WarnerMedia with Discovery, forming Warner Bros. Discovery, was completed on the 8th of April 2022.