How did the Marvel Comics multiverse begin?

Within Marvel Comics, most stories take place within a shared universe that is part of a larger multiverse, with the main continuity designated as Earth-616 starting from a Captain Britain story in The Daredevils. Other writers expanded the concept through various titles, while time-traveling characters spun out new alternate timelines. The concept later became a focal point for the Marvel Cinematic Universe across its Multiverse Saga.

What we know

• Most stories in Marvel Comics take place within the Marvel Universe, which is part of a larger multiverse. [1, 2]
• The main continuity in which most Marvel storylines take place was designated as Earth-616, starting with a Captain Britain story in The Daredevils #7. [2]
• New universes spin out of storylines involving time-traveling characters such as Rachel Summers, Cable, and Bishop. [2] · medium confidence
• Organizations like the Captain Britain Corps, Council of Watchers, Exiles, Council of Reeds, and the Time Variance Authority attempt to safeguard and protect the multiverse. [2]

Where to go next

• a case in pointWhat is Earth-616 in Marvel continuity?
• how it workedHow does the Time Variance Authority protect the timeline?
• what caused itWhat caused the Multiverse Saga in the MCU?
• how we knowHow did Doctor Strange introduce alternate dimensions?
• the bigger pictureWhat are shared fictional universes?
• an unexpected connectionHow did a Captain Britain comic establish Earth-616?The foundational designation for Marvel's primary reality originated in a Captain Britain story rather than a mainstream Avengers or Spider-Man title.

Sources

• [1]Multiverse (Wikidata Q598824) · CC0 1.0
• [2]Multiverse (Marvel Comics) · CC BY-SA 4.0
• [3]Marvel Cinematic Universe: Phase Six · CC BY-SA 4.0
• [4]Multiverse (Marvel Cinematic Universe) · CC BY-SA 4.0
• [5]Wanda Maximoff (Marvel Cinematic Universe) · CC BY-SA 4.0