Earliest story with Esperanto future

Question

Can anyone help identify the earliest piece of fiction to show a future where Esperanto is widespread?

Here are the two candidates I can propose up front.

"Homo Sol", written Jan. 1, 1940, short story by Isaac Asimov. An extraterrestrial character is quoted saying "I delivered the invitation before their parliament in their own language–a simple one they call Esperanto." There were some things this character didn't know about Earth, but I'm sure he did enough research to know the language, so I'm confident this counts.

"The War in the Air", written in 1908, novel by H.G. Wells. It has this quote "Bert came to houses of the same detached, unwalled, wooden type, but adorned now with enamelled advertisements partly in English and partly in Esperanto." The novel does not say whether Esperanto ads are common in the future, or whether it's just the habits of one eccentric shopkeeper. Esperanto is certainly not overwhelmingly popular, because this novel has a lot of language barriers between people speaking English, French, German, and Czech. I don't know whether this counts or not without looking more into what the author intended.

Things that are out of scope for this question (but interesting enough for me to be curious about them)

• Non-fiction predictions
• Using Volapük or a fictional auxiliary language
• Using Esperanto as a stand-in for another language, like in the comic book series "Saga"
• Works not set in the author's future, like the movie "The Great Dictator", which features fictitious countries
• Works where Esperanto is no more widespread than it was in the author's time

Related questions on Esperanto Stack Exchange: Use of Esperanto in Science Fiction, which asks for a list of science fiction works featuring Esperanto, without asking for earliest, and without specifying that Esperanto be widespread in the future.

Ĉu estas iu ajn sciencfikcia filmo en kiu troviĝas Esperanto?, which is like the above, but it's only about films.

Answer 1

1907: Lord of the World, a novel by Robert Hugh Benson, first published by Dodd, Mead in 1907, available at Project Gutenberg.

From the Wikipedia page for Lord of the World:

Lord of the World is a 1907 dystopian science fiction novel by Monsignor Robert Hugh Benson that centers upon the reign of the Anti-Christ and the End of the World.

[. . . .]

Writing during the pontificate of Pope Pius X and prior to the First World War, Monsignor Benson accurately predicted interstate highways, weapons of mass destruction, the use of aircraft to drop bombs on both military and civilian targets, and passenger air travel in advanced Zeppelins called "Volors". Writing in 1916, Fr. Martindale compared Mgr. Benson's ideas for future technology with those of legendary French science fiction novelist Jules Verne.

[. . . .]

Nationalism has been destroyed by Marxist internationalism and the world has been divided into three power-blocs. The first, which is generally marked in red on maps, is a European Confederation of Marxist one-party states and their colonies in Africa that use Esperanto for a world language. The second, marked in yellow, is "the Eastern Empire", whose Emperor, the "Son of Heaven", descends from the Japanese and Chinese Imperial Families. The third, the blue marked, "the American Republic", consists of North, South, and Central America.

Excerpts from Lord of the World:

Since yesterday I have a little more information. It appears certain that the Bill establishing Esperanto for all State purposes will be brought in in June. I have had this from Johnson. This, as I have pointed out before, is the very last stone in our consolidation with the continent, which, at present, is to be regretted. . . .

[. . . .]

"Of his actual words we have nothing to say. So far as we are aware no reporter made notes at the moment; but the speech, delivered in Esperanto, was a very simple one, and very short. It consisted of a brief announcement of the great fact of Universal Brotherhood, a congratulation to all who were yet alive to witness this consummation of history; and, at the end, an ascription of praise to that Spirit of the World whose incarnation was now accomplished.

[. . . .]

He had congratulated him upon his Latin then—for they had spoken in that language throughout this second interview; and Percy had explained how loyal Catholic England had been in obeying the order, given ten years before, that Latin should become to the Church what Esperanto was becoming to the world.

1908: "The Planet Juggler", a novelette by J. George Frederick; first published in The All-Story Magazine, November 1908; reprinted in Famous Fantastic Mysteries, March 1940, which is available at the Internet Archive.

From Everett F. Bleiler's review in Science-Fiction: The Early Years:

One of the very earliest space operas, setting many of the patterns of later work. * World peril and interstellar war. * Unspecified future, far enough away that Esperanto has become the world language. * A startling message reaches the earth: "Deliver to me five hundred million tons of gold, or else I will drop the earth into the sun." Conversation reveals that the threat-maker is a native of Canopus, and that he has learned Esperanto by monitoring earth for the past ten years. (It is also revealed later that gold is in short supply on Canopus, and that the entity needs it to build an interstellar empire. He plans to exterminate the lesser races of the universe.)

Excerpt from "The Planet Juggler":

"Hallo, Earth! Hallo, Earth! Do you understand? Hallo, Earth! Hallo, Earth!" — and ran on indefinitely, in Esperanto, the universal language which was by this time used by all the intelligent classes of the earth.

Answer 2

Maybe not the earliest, but one of the Stainless Steel Rat books by Harry Harrison (the second one, I believe) had Slippery Jim find himself pointing a weapon at a barman who squeaks "Ne mortigu min!"

Slippery Jim then goes off on an internal monologue about how much he approves of Esperanto being used as a universal language in the milieu around which he is prancing.

That would be somewhere in the mid-60s.