The millennium
"In 1907, Upton Sinclair looked forward 93 years and imagined the year 2000, when capitalism would find its zenith with the construction of The Pleasure Palace, a glittering 100-story-high structure in the middle of New York's Central Park. During the grand opening of the towering building, a scientific experiment with radiumite explodes, killing everybody throughout the world except eleven people at the Pleasure Palace.".

"These survivors struggle to rebuild their lives by creating a new capitalistic society. After that fails, along with several other efforts, they create a utopian society on the lush grounds of a grand country estate in the Pocantico Hills above the Hudson River, embodying Sinclair's life-long vision of "The Cooperative Commonwealth.""--BOOK JACKET.
Fiction, Utopias, Two thousand, A.D., Millennium (Eschatology), End of the world
Upton Sinclair
Upton Sinclair, Jr., was a Pulitzer Prize-winning American  author who wrote over 90 books in many genres. He achieved popularity in the first half of the 20th century, acquiring particular fame for his 1906 muckraking novel The Jungle. It exposed conditions in the U.S. meat packing industry, causing a public uproar that contributed in part to the passage a few months later of the 1906 Pure Food and Drug Act and the Meat Inspection Act.
--Wikipedia