The arrival of Father Junipero Serra, founder of the California mission system. In 1769, San Diego was permanently settled for the first time in what was referred to as the "Sacred Expedition". It was led by able bodied Captain Gaspar de Portola and included monks of the Franciscan order. Most notable of these was the sharp-tongued Father Junipero Serra. On July 16, Serra offered his first mass overlooking what would become present day Old Town. The building of a fortification known as the Presidio started that same month. Serra continued to mastermind the founding of a chain of missions throughout California. It is these missions that most people instantly think of when visualizing Old California.