Dating back to the 16th century, the Spanish people thought that the “Baja California Peninsula” was not part of mainland North America, but a large island separated from the mainland by the so-called “Gulf of California”.
Thus, the Island of California refers to a European misconception, which was one of the most famous cartographic errors in human history. This misconception was then spread to many countries and was copied into many maps despite contradictory evidence from sailors.
In addition, there were other misconceptions about California, one of them was the idea that California was a terrestrial paradise or heaven, like the Garden of Eden and Atlantis. The first known mention of the “Island of California” was in the 1510 romance novel; Las Sergas de Esplandián by Garci Rodríguez de Montalvo.
It was in 1539 when Hernan Cortés sent a navigator named Francisco de Ulloa to the so-called “Island of California”, and they found that the Baja California Peninsula is a peninsula and not an island. Ulloa reached the mouth of the Colorado River at the head of the gulf, which seemed to prove the fact that Baja California was a peninsula. However, it was only after an expedition by Hernando de Alarcón that it was officially proven that Baja California is a peninsula.