* Nineteenth Century: Tolkien began writing the story in the 1930s, which would fall within the 20th century, but he conceptualized the world of Middle-earth and its history during his time at Oxford University in the 1910s, which was part of the 19th century.
* Twentieth Century: He published "The Hobbit" in 1937 and later expanded it into the epic "Lord of the Rings" trilogy, publishing it in 1954, 1954, and 1955.
* Twenty-First Century: Tolkien's work has continued to be developed through:
* The publication of "The Silmarillion" and other posthumous works which delve deeper into Middle-earth's history.
* Adaptations: Peter Jackson's film trilogy (2001-2003) and Amazon's "The Lord of the Rings: The Rings of Power" TV series (2022-present) continue to expand the story's reach.
Therefore, "The Lord of the Rings" is a novel with origins in the 19th century and has been further developed in the 20th and 21st centuries.