Island of California

In 1535, Cortés arrived in the bay there and named the area Santa Cruz; he attempted to start a colony but abandoned his efforts after several years due to logistical problems.

[5] Carmelite friar Antonio de la Ascensión [es], a priest at the top of the Spanish church, was the first known person to depict California as an island in 1603.

[12] On the return voyage to Acapulco, Mexico, Friar Antonio's ship was overtaken by Dutch pirates who found and confiscated a map drawn by him that depicted California as an island, effectively leaking state-secret information.

At the bottom left corner of a British map from 1630 drawn by Henry Briggs is scribbled "California, sometimes supposed to be a part of the western continent, but since by a Spanish chart taken from Hollanders, it is found to be a goodly island".

De Fuca claimed to have explored the western coast of North America and to have found a large opening that possibly connected to the Atlantic Ocean — the legendary Northwest Passage.

Finding a Northwest Passage was something that motivated many of the explorers coming to the California coast at the time, as it would be extremely profitable for Europe if a northern trade route to Asia could be found.

"[16] However, Cook describes some bad weather in his account around this time, and did continue on to map most of the outer Pacific coastline of North America from modern-day northern California to the Bering Strait in Alaska on the same voyage.

Reports from Oñate's expedition reached Antonio de la Ascención, a Carmelite friar who had participated in Sebastián Vizcaíno's explorations of the west coast of California in 1602 and 1603.

He made a series of overland expeditions from northern Sonora to areas within or near the Colorado River's delta in 1698–1706, in part to provide a practical route between the Jesuits' missions in Sonoran and Baja California but also to resolve the geographical question.

The first report of Kino's discovery and his map from 1701 showing California as a peninsula were sent to Europe by Marcus Antonius Kappus, a Jesuit missionary from Kamna Gorica (Duchy of Carniola, now Slovenia).

Jesuit missionary-explorers in Baja California who attempted to lay the issue finally to rest included Juan de Ugarte (1721), Ferdinand Konščak (1746), and Wenceslaus Linck (1766).