In 1769, the Portola expedition traveled north by land from San Diego, seeking to establish a base at the Port of Monterey described by Sebastian Vizcaino in 1602.

The party reached San Pedro Creek on October 31 and camped there for four nights, while scouts led by José Francisco Ortega climbed Sweeney Ridge, where they could see over the ridge toward the east, and so became the first Europeans to see San Francisco Bay on November 1.

Franciscan missionary Juan Crespi noted in his diary, "from the summit of a peak we beheld the great estuary or arm of the sea.

Sweeney Ridge is located in northern San Mateo County and is now a part of the Golden Gate National Recreation Area.

[3][2] The spot chosen for the marker is somewhat arbitrary, as the precise location where Portola's party reached the summit of the ridge is not known.