San Francisco Bay is an important harbor on the American West Coast and one of the greatest naturally formed, sheltered anchorages in the world. The San Francisco Bay Discovery Site marks one of the greatest events in the establishment of Spanish Alta California -- the moment the Spanish first glimpsed the bay. On November 4, 1769, Captain Juan Gaspar de Portolá and members of his overland exploration expedition climbed to the top of Sweeney Ridge and looked out upon the great bay. The discovery ultimately led to the establishment of San Francisco, one of the nation’s most vibrant cities.

The top of the ridge is now known as the San Francisco Bay Discovery Site, a National Historic Landmark and part of the Golden Gate National Recreation Area. Visitors have the chance to follow the footsteps of Spanish explorers, soldiers, and early colonists as they climb the ridge and view the magnificent bay for themselves.

The history of the Spanish discovery of the site begins with an accident. Spanish Explorer Captain Juan Gaspar de Portolá set out from San Diego with a party of 60 men on horseback. His goal was to head north and find Monterey Bay, which had been described only from ships at sea. When Portolá’s land-based expedition arrived at the Monterey Bay and stood on its sands – they failed to recognize the bay! Instead Portolá pressed northward on a long, treacherous mission to look for a bay he had already passed by.

Captain Juan Gaspar de Portolá is credited as the first European to recognize the San Francisco Bay, today one of the most important ports in the world. Public Domain

Exhausted and lost, the group eventually climbed over San Pedro Mountain and made camp in Pedro Valley, now in the city of Pacifica, just south of San Francisco. On November 1, 1769, one of Portolá’s men, José Francisco Ortega, led a squad of scouts on a three-day reconnoitering tour of the forested area surrounding the camp. Ortega’s notes show he sighted the San Francisco Bay on his first day of scouting, but assumed it was an estuary. When Ortega returned to camp, Portolá called for further exploration of the “estuary” and on November 4, 1769, the men climbed to the top of modern-day Sweeny Ridge hoping for a better view.

Here they first recognized that the body of water they glimpsed was a massive, sheltered bay – a discovery that numerous Spanish sea expeditions in the region had never made. Portolá himself wrote that there appeared to be, “...a large arm of the sea…some sort of harbor there within the mountains.” The Spanish were not excited about the historic discovery at the time, however, as Portolá realized he had mistakenly passed by Monterey, his original destination, over a hundred miles to the south. The entire expedition returned homeward, and Captain Portolá would ultimately find Monterey Bay and found the presidio there in 1770. For more about Monterey, click here.

Although the original European discovery of San Francisco Bay was a disappointment to Portolá, the Spanish quickly recognized the strategic value of such a huge, sheltered harbor. By 1776, they established the Presidio of San Francisco under the leadership of Captain Juan Bautista de Anza. The military fort would serve as protector of the bay for the next two centuries under Spanish, Mexican, and American flags. The San Francisco Presidio is also featured in this itinerary and its history can be explored here.

The Portolá expedition discovered the bay completely by accident from the top of Sweeny Ridge Courtesy of the National Park Service, Morton Kunstler

The San Francisco Bay Discovery Site’s historic significance was officially recognized in 1968 when it became a National Historic Landmark. The National Park Service erected a marker made of California’s State stone, Serpentine, at the peak of Sweeny Ridge. The monument pays honor to the Portolá Expedition’s important discovery. Today the site consists of approximately 18.5 acres of protected land that surrounds the two small knolls where the Spaniards originally spotted the bay. The visual impact of the site is its superb view. At the top of Sweeny Ridge, visitors are privy to the same breathtaking vista that Portolá saw centuries ago--the tremendous expanse of the Bay area spread beneath them and the coastline north as far up as Point Reyes.

The San Francisco Bay Discovery Site is part of the Golden Gate National Recreation Area–one of the world’s largest urban national parks. In addition to Sweeny Ridge, the park is home to more than 30 scenic and historic sites, displaying a veritable cross section of California’s history throughout the Spanish, Mexican and early American eras. From forested hiking trails to Civil War era barracks, Golden Gate Recreation Area has something to offer all visitors.