In 1769 Father Junípero Serra founded San Diego after occupying the Kumeyaay village of Kosa'aay and created the first of the California missions, Mission San Diego de Alcalá. The Valley of Tijuana was explored the same year by Juan Crespí. In 1829 Santiago Argüello, a Californio and a major Mexican land grant ranchos owner, obtained ownership of a parcel of land known as Rancho Tía Juana and in 1889 was Tijuana officially founded on this parcel when descendants of Argüello and Agustin Olvera, an early Los Angeles pioneer, agreed to develop the city.