Complex sentence: A Spanish exploration party, led by Don Gaspar de Portolà, arriving on November 2,1769, was the first documented European visit to San Francisco Bay, claiming it for Spain as part of the Viceroyalty of New Spain.
Split into simpler sentences: A Spanish exploration party, led by Portolà and arriving on November 2,1769, was the first documented European sighting of San Francisco Bay. Portolà claimed the area for Spain as part of the Viceroyalty of New Spain.