The online repository is expected to attract viewers interested in early California history, or at least the imaginations of European explorers of the region. Spurred in part by fantastical descriptions in an early 16th century novel, Spanish travelers originally searched for an island supposedly populated by cannibalistic Amazons with plentiful jewels and gold.
You can view some of the maps in a slide show at http://news.stanford.edu/news/2012/august/slideshow/12825.html. You can learn more at http://lib.stanford.edu/california-as-an-island.
Most of the earliest maps depict California as an island. "Better get ready to tie up the boat in Idaho."