Did DC invent the multiverse concept decades before Marvel?

The answer

In September 1961, writer Gardner Fox and artist Carmine Infantino published 'Flash of Two Worlds' in The Flash #123, introducing the concept of parallel Earths to superhero comics. The story featured Barry Allen, the modern Flash, vibrating at super-speed and accidentally traveling to Earth-Two, where the original 1940s Flash Jay Garrick existed. This single issue established DC's multiverse, predating Marvel's own exploration of parallel realities by years. The concept became so central to DC that annual Justice League crossovers between Earth-One and Earth-Two began in 1963, eventually spawning the landmark 1985 series Crisis on Infinite Earths. Today, the multiverse concept dominates blockbuster cinema from Spider-Verse to Everything Everywhere All at Once.