So I know Heinlein had an early story from the 40s. Elsewhen 1941.
It was recently mentioned comics added the multiverse in 1961.
Was there a story before Elsewhen?
H.G. Wells, A Modern Utopia (1905)?
He calls the parallel universe another planet, parallel to Earth including individual people, and the portal is in the Swiss Alps.
~Max
More philosophy than literature, but still…
Depends greatly on how you decide to define the terms.
Many utopias were set in hidden or imaginary places that paralleled our current world. More’s Utopia was set in “no place.” The far less known Uchronie (1876) by Charles Bernard Renouvier coined the term for meaning “no time” and was used for an imaginary past.
The Science Fiction encyclopedia has this under the term Parallel Worlds:
Notable early sf extrapolations include J-H Rosny aîné’s Un autre monde (1895 Revue Parisienne #5; exp as coll 1898; trans as “Another World” in A Century of Science Fiction, anth 1962, ed Damon Knight) – whose “other world” is not truly separate from Earth but merely hidden from normal human perception – and two stories by H G Wells: “The Remarkable Case of Davidson’s Eyes” (28 March 1895 Pall Mall Budget) and “The Plattner Story” (April 1896 The New Review).
Wells loved the idea and used it regularly. His Men LIke Gods (1923) uses the term explicitly.
We conceive ourselves to be living in a parallel universe to yours, on a planet the very brother of your own.
Preceding him was Gerald Grogan’s 1915 A Drop in Infinity, which played around with both parallel worlds and a multiverse but apparently didn’t develop them much.
Pretty much everybody credits Murray Leinster’s Sidewise in Time (1934) as the first modern science fiction example and the one that everybody in the field copied from.
If you expand the search to religion and philosophy, the notion has been bruited about since forever, as given in The Multiverse Is an Ancient Idea, but I’d argue that we’re pasting modern terms and ideas onto vague similarities just for the sake of pushing “earliest” back as far as possible. On review, that article is similar in concept to the one posted by @Elmer_J.Fudd.
The gospels.
Heinlein also had Glory Road which involved multiple universes. And tried to wrap up his whole character list with the disasterous Number of the Beast. God that was a bad book.
Only goes back to 1970 but I think Roger Zelazny’s Nine Princes in Amber was my first exposure to the concept of a multiverse (albeit a different take on it than usual).
Long ago I remember there was a web site that had a timeline with an exhaustive list of Alternate Histories both by publication and point of divergence dates. My memory is it had publication entries going back to the turn of the previous century if not earlier. One of the earliest was an essay about if a certain battle had gone a different way than reality. I wish I can remember the details or the site.
This page lists alternate histories written before the genre could be considered a genre.
Arguments can be made for a number of possible dates marking a possible genre beginning (see, e.g., Winthrop-Young’s “Fallacies and Thresholds”), from the 1931 publication of J.C. Squire’s anthology If It Had Happened Otherwise to the 1953 publication of Ward Moore’s Bring the Jubilee. The date chosen here is 1939, the year that L. Sprague de Camp’s original short story of “Lest Darkness Fall” saw publication, an event which effectively made alternate history fiction a sub-genre of science fiction.
The increasing number of alternate histories which saw publication from the mid-1930s on are presumably a result of the generally respectful treatment given the subject by the essayists in Squire’s If It Had Happened Otherwise and by historian Albert Toynbee in three essays included in his A Study of History.
The first allohistorical novel would seem to be Geoffroy-Château’s Napoléon et la conquête du monde, 1812-1823: histoire de la monarchie universelle (1836). Although Benjamin Disraeli’s The Wondrous Tale of Alroy (1833) predates that work, there is serious question whether Alroy is truly allohistorical.
The earliest allohistorical short story is apparently Nathaniel Hawthorne’s “P.'s Correspondence” (1845).
Other pre-1850 items listed below are not entirely alternate history but contain allohistorical digressions within larger works.