Our main character, Karana, is a native of an island about 75 miles off the coast of Southern California, who gets left behind when the people of her village are taken away to the mainland. Though her home is called Island of the Blue Dolphins, we know that O'Dell based the setting on San Nicolas Island. This is because the story is based on the true story of the Lone Woman of San Nicolas Island, a real woman who, just like Karana, who was left alone on a remote island.
But why is the setting of a desert island so important? Well, for a couple of reasons, we think. First, the novel is trying to figure out humans' relationship to nature. What better place to do that than when surrounded by nature itself: a desert island filled with dolphins and dogs and devilfish? Karana is totally separated from other people and so she has the time and space to imagine a new kind of relationship with nature – a relationship a little less violent than the ones that came before her. In this way, the setting helps the author develop one of the novel's major themes.
The desert island setting also makes the book seem more mysterious and exciting. This is, you know, an adventure novel. And what better place to have adventures than on an exotic island in the middle of the ocean? It's kind of like Treasure Island or something. The remote location makes the plot more suspenseful – will Karana ever make it to the mainland? Will she ever be rescued from the island?