The Spanish explored the coastal area of Alta California by sea beginning in the 16th century and prospected the area as a domain of the Spanish monarchy. During the following two centuries there were various plans to settle the area, including Sebastián Vizcaíno's expedition in 1602–03 preparatory to colonization planned for 1606–07, which was canceled in 1608.
Between 1683 and 1834, Jesuit and Franciscan missionaries established a series of religious outposts from today's Baja California and Baja California Sur into present-day California. Father Eusebio Kino missionized the Pimería Alta from 1687 until his death in 1711. Plans in 1715 by Juan Manuel de Oliván Rebolledo resulted in a 1716 decree for extension of the conquest (of Baja California) which came to nothing. Juan Bautista de Anssa proposed an expedition from Sonora in 1737 and the Council of the Indies planned settlements in 1744. Don Fernando Sánchez Salvador researched the earlier proposals and suggested the area of the Gila and Colorado Rivers as the locale for forts or presidios preventing the French or the English from "occupying Monterey and invading the neighboring coasts of California which are at the mouth of the Carmel River." Alta California was not easily accessible from New Spain: land routes were cut off by deserts and often hostile Native populations and sea routes ran counter to the southerly currents of the distant northeastern Pacific. Ultimately, New Spain did not have the economic resources nor population to settle such a far northern outpost.
Spanish interest in colonizing Alta California was revived under the visita of José de Gálvez as part of his plans to completely reorganize the governance of the Interior Provinces and push Spanish settlement further north. In subsequent decades, news of Russian colonization and maritime fur trading in Alaska, and the 1768 naval expedition of Pyotr Krenitsyn and Mikhail Levashev, in particular, alarmed the Spanish government and served to justify Gálvez's vision. To ascertain the Russian threat, a number of Spanish expeditions to the Pacific Northwest were launched. In preparation for settlement of Alta California, the northern, mainland region of Las Californias was granted to Franciscan missionaries to convert the Native population to Catholicism, following a model that had been used for over a century in Baja California. The Spanish Crown funded the construction and subsidized the operation of the missions, with the goal that the relocation, conversion and enforced labor of Native people would bolster Spanish rule.
The first Alta California mission and presidio were established by the Franciscan friar Junípero Serra and Gaspar de Portolá in San Diego in 1769. The following year, 1770, the second mission and presidio were founded in Monterey. In 1773 a boundary between the Baja California missions (whose control had been passed to the Dominicans) and the Franciscan missions of Alta California was set by Francisco Palóu. The missionary effort coincided with the construction of presidios and pueblos, which were to be manned and populated by Hispanic people. The first pueblo founded was San José in 1777, followed by Los Ángeles in 1781. (Branciforte, founded in 1797, failed to maintain enough settlers to be granted pueblo status.)