De Portolá, a Catalonian nobleman, served in the Spanish army before being appointed the governor of Baja California in 1767, in order to expel the Jesuit missionaries there.
In 1769, he lead an expedition set out to establish a Spanish colony at Monterey Bay. The expedition's four parties met at San Diego Bay, where colony - the present-day San Diego - was established. De Portolá's land party initially didn't find the bay and returned to San Diego. A second expedition was set out, and Monterey Bay was finally reached on May 24, 1770. There, the mission of San Carlos was founded.
De Portolá later became governor of Puebla, and returned to Spain in 1784, after which nothing is known about him.