The maps come from a new collection of 800 "California as an island" maps at the Stanford Libraries. They collected by Glen McLaughlin, one of the nation's top map collectors.
"To my knowledge, it is the largest collection featuring California as an island in private hands in the world," said McLaughlin. "The collection was built over a 40-year time period, from 1971 to last year."
"California and the Northwest coast of America was one of the unexplored places on Earth, along with Antarctica and Australia," McLaughlin said in a statement from Stanford University.
Here's how it started, from the Stanford release:
The earliest Spanish maps from the 16th century show a continuous coastline, but a Carmelite friar, Antonio de la Ascensíon, accompanied Sebastian Vizcaíno on his West Coast expedition of 1602-03 and apparently drew a map depicting California as an island around 1620.
Plunder was commonplace, and Spanish maps were a hot commodity. They were also a state secret. It's generally accepted that the Dutch captured a ship en route, and the charts were waylaid to Amsterdam. What we know for sure is that the maps were widely copied.
Perhaps it's just what the Spanish wanted, suggested [says Stanford Library fellow Rebecca] Solnit. "I've been told that Spain knew it wasn't an island, but it was politically expedient for others to think it was. They weren't going to share what they knew with everybody else."
Enough was enough in 1747, when King Ferdinand VI of Spain issued a royal decree proclaiming, "California is not an island."
The representation of California as an island was present on a few Asian maps even into the 1860s. Here are several of the maps showing California as an Island that Glen McLaughli picked out as iconic maps from the collection.