Events › The De Anza Expedition and Spanish Colonization of Alta California, 1769-1776

The year 2026 marks the 250th anniversary of the Declaration of Independence. Closer to home, it marks the 250th anniversary of the expedition of Juan Bautista de Anza, and the resulting colonization of Upper California by the Spanish. This event had a profound effect on the history of what would become Contra Costa County, and is therefore the subject of programs, talks, and discussions involving the many historical societies within the County. Your El Sobrante Historical Society is naturally part of that activity.

Part I: Elusive Ports

Tuesday January 27 at 6:30 pm, Presenter:  Donald Bastin

The strange and unlikely story of the search for the harbors of Monterey and San Francisco and the founding of the Mission and Presidio of San Francisco 1769-1776.

For 250 years, the Spanish crown had virtually ignored its claimed holdings in Upper California, and may have continued in this attitude had it not been for a confluence of factors which led, in 1768, to the planning of a series of expeditions of discovery in this mostly uncharted territory. This is the story of that effort, full of hardship, disappointment, and surprise, including a harbor that could not be found, and the fateful and unexpected discovery of a magnificent bay which, strangely, already bore the name of the patron saint of the Franciscan order.

This is not a celebration of the Spanish occupation of Upper California. But that event is part of our history, and it is important that we know that history, just as it is important that we know and understand the history of the birth of our country, with all its warts and imperfections. 

Part II: Joaquin Ysidro de Castro

Saturday January 31 at 1:00 pm, Presenter:  Roxy Miraválle

Pvt. Joaquin Ysidro de Castro, patriarch of Francisco Castro (grantee of Rancho San Pablo) and his ties to the Anza Expedition.

As the soldiers of Anza’s expedition were the founders and first settlers of Alta California, it becomes a matter of historical importance to know who they were. They left their imprint on the civilization of California, and their names are as familiar as household words to all who know the state’s history. One of these early pioneer soldiers was a recruit named Joaquín Ysidro de Castro, patriarch of the grantee of our own San Pablo rancho. Castro and the family which accompanied him on this expedition are among the founding settlers of the Presidio de San José, which were established as a result of this expedition.

For special accommodations, please give the library 72 hours notice. Light refreshments provided with the generous support of Friends of El Sobrante Library.