Pastwatch
From back cover Tor paperback February 1997:

In one of the most powerful and thought-provoking novels of his remarkable career, Orson Scott Card interweaves a compelling portrait of Christopher Columbus with the story of a future scientist who believes she can alter human history from a tragedy of bloodshed and brutality to a world filled with hope and healing.
Fiction, Christopher columbus in fiction, Discoveries in geography, Discoveries in geography in fiction, Time travel in fiction
Orson Scott Card
Orson Scott Card is an American novelist, critic, public speaker, essayist and columnist. He writes in several genres but is known best for science fiction. His novel Ender's Game (1985) and its sequel Speaker for the Dead (1986) both won Hugo and Nebula Awards, making Card the only author to win both science fiction's top U.S. prizes in consecutive years.