The San Francisco Bay Discovery Site, a National Historic Landmark, marks the site on top of Sweeney Ridge, where, in 1769, members of Gaspar de Portolo's overland exploration expedition first saw the San Francisco Bay. Following this momentous discovery by the Spaniards, a presidio and two missions were established in what is now San Francisco.

The San Francisco Bay Discovery Site is located four miles west of San Bruno via Skyline Dr., in San Mateo County. The Sweeney Ridge Trail leads you 2.5 miles from Skyline College south past the Nike Missile Site ruins to the Discovery Site. To get there, take Skyline Blvd. (Hwy. 35) to College Dr. in San Bruno. Go west on College Dr. until you reach Skyline College, then turn left at the "T" junction. The trailhead is at parking lot #2. Go to the top of "the notch" where part of the Nike control station stands, then descend into a riparian corridor and up again to an intersection with the Mori Ridge trail. Turn left (east), and you'll soon be walking on a former U.S. Army road past the Nike site ruins. The road eventually turns left and downhill, but continue straight onto the dirt trail. The first jog on the left takes you to the Discovery Site and its three stone monuments. Sweeney Ridge is part of the National Park Service's Golden Gate National Recreation Area.