Almonroth on Wikimedia Commons

First Ship into San Francisco Bay On August 5, 1775, the Spanish packet San Carlos, under the command of Lieutenant Juan Manuel de Ayala, became the first ship to enter San Francisco Bay. A month and a half was spent in surveying the bay from its southern most reaches to the northern end of present-day Suisun Bay. The San Carlos departed September 18, 1775. California Historical Landmark No. 236