Gaspar de Portolá’s discovery of San Francisco Bay on November 4, 1769, was Spain’s most significant discovery in North America during the 18th century. It prompted a new strategy on how it would use its mission system to colonize Alta California. The historical ramifications of these plans have had an impact down to the present day. For the native people, who had successfully managed the California environment for thousands of years, the event marked the beginning of the end of their way of life. This discovery took place on Sweeney Ridge, which stretches between today’s Pacifica and San Bruno. As a result, San Mateo County will celebrate the 250th anniversary of this pivotal moment in western history with the creation of a historical and recreational trail tracing the path of Portola on the San Francisco Peninsula.