One of the most interesting cartographic myths of the European exploration of the Americas was California shown as an island. This famous misconception impacted the accuracy of mapmaking for over a hundred years, until its acceptance as part of the mainland was established in the mid eighteenth century.
Between the years 1500 and 1747, a lot of confusion ensued over whether or not California, a mysterious land with an abundance of gold, was in fact an island. As early as 1500, California was thought to be an island. As more and more explorers ventured into the coastal region, it was established that California was, in reality, a peninsula. This discovery, however, did not last long as miscommunications and mistaken observations turned the coast back into an island.
Beginning in the year 1622, California began its cartographic existence as a large island off the coast of Nouveau Mexique. It appeared to have a rough and rocky coastline complete with smaller islands off the shore. The theory became universally accepted over the next ten years as influential publishers such as Nicolas Sanson, Guillaume Blaeu and Pierre DuVal created beautiful maps that confirmed California's insularity. Some maps even highlighted a fictional Northern coast with finger-like peninsulas reaching towards the mainland.
Although Father Eusebio Kino confirmed that California was part of the landmass of America in the early eighteenth century, it was not until 1747 when Ferdinand VII of Spain declared it part of the mainland that cartographers began to eliminate the myth.