Gaspar de Portola’s expeditions came at a turbulent time for the Western United States. Several groups were vying for resources in areas like Southern California for various reasons. England would have been able to expand from the East Coast and capture territory on both sides of the vast continent. Spain had already seen them conquer Canada, and was not willing to concede the territory they held north through Mexico.
Russia was also a threat. Their fur trappers were working their way south from Alaska.
So de Portola was dispatched along with Father Juan Crespi to establish missionaries in the area meant to hold territory and work with natives. He sailed to San Diego Bay in 1769, where he left on foot in May of the same year toward Monterey Bay. Errors in navigation and weather caused ships to veer off course, which delayed one shipment of soldiers and priests and wiped out another ship carrying supplier. The expedition set out in spite of these unlucky set backs
The first site they found was present day Los Angeles, which led them down a Native American trail we would recognize today as Wilshire Boulevard. It was Crespi who named a creek Santa Cruz, and the team passed through the San Francisco Bay Area finding the site we know of as the Golden Gate Bridge.
Gaspar did reach Monterey Bay, but weather obscured his view and he thought he missed it. He returned home with detailed descriptions of what he did find. He was informed that he had, in fact, found Monterey. Determined perhaps to prove himself right (or them wrong) he set out again where he did finally find Monterey.