Island of the Blue Dolphins is based upon a real story in which the Lost Woman of San Nicolas lived alone on an island from 1835 to 1853. Karana is a twelve year-old girl living on the Island of Blue Dolphins, located about 75 miles southwest of present day Los Angeles. Her people, the people of Ghalas-at, are visited by explorers from the Aleutians (Russians) who come and bargain for the ability to hunt sea otters. The Aleutians leave without paying the people of Ghalas-at. As they leave, there is a battle. Karana's father, Chief Chowig is killed during the battle. Chief Chowig's successor, Kimki leaves the island to look for a new place to live. Time passes and white men arrive saying they will take the villagers to a new home. Karana jumps ship when she realizes that her brother, Ramo, is still on the island. The ship leaves with everyone except Karana and Ramo. Shortly thereafter, Ramo is killed by wild dogs and Karana is left alone.
The plot of the novel begins with the migration of the villagers to a new home and the second section of the plot focuses on Karana's resourcefulness in surviving alone: how she finds shelter, food, and how she intends to exact her revenge on the wild dogs. She eventually forms a family by taming some wild animals, even the dog that was the leader of the pack that killed her brother. In this sense, Karana transitions from living in fear and for revenge to living in harmony with her environment. She determines to kill less and tries to live with, rather than in domination over, the world around her. In this way, the novel is about Karana's maturity and self-reliance but it is also a plot about respecting and admiring nature.
It isn't until the end of the novel (18 years living alone) that Karana discovers that the ship carrying her people had sunk and this is why it never returned to get her.
Not until I came to Mission Santa Barbara and met Father Gonzales did I learn from him that this ship had sunk in a great storm soon after it reached his country and that on the whole ocean thereabouts there was no other.
In the author's note at the end of the book, the author adds that this is a "girl Robinson Crusoe" based on real events: The Lost Woman of San Nicolas.