strait, in California, western coastal U.S., connecting San Francisco Bay with the Pacific Ocean and separating San Francisco from Marin County. An ancient river mouth, it is about 3 miles (5 km) long, from 1 to 3 miles wide, and 300 feet (90 m) deep and serves as the ocean gateway to the port cities of the bay and the Sacramento–San Joaquin river system. The strait, now spanned by the Golden Gate Bridge (see photograph-->), was probably seen by Sir Francis Drake in 1579, but the actual European discovery of it was made in 1769 by a land party led by Francisco de Ortega. In 1775 the San Carlos, navigated by Juan Manuel de Ayala, was the first European ship to sail through the strait. The name Golden Gate was given in 1846 by Captain John C. Frémont in analogy to the Golden Horn of the Bosporus (Turkey) when he visualized rich cargoes from the Orient flowing through the strait.