Background: Why Spain Sent the Expeditions

By the mid-1700s, Spain’s empire in the Americas stretched impressively from the tip of South America through Mexico and into the deserts and mountains of today’s U.S. Southwest. Yet at the empire’s northern edge, Spanish control was fragile. Russian fur traders were pushing south along the Pacific Coast, and English explorers were probing the same waters, eager to claim new footholds. To Spanish officials, the fear was clear: if they did not occupy these distant northern lands, someone else would.

At the same time, Spain’s colonial government was undergoing major reforms known as the Bourbon Reforms – a sweeping effort to tighten imperial control and modernize administration across its colonies. One of the leading architects of these reforms was José de Gálvez, the Visitador General of New Spain, a determined and ambitious official charged with revitalizing Spain’s northern frontier. Gálvez envisioned a chain of new settlements and defenses in Alta California, the sparsely occupied region that would one day become the state of California.

His strategy combined faith and force. Spain would secure its claim through a network of presidios (military forts) to protect the land, and missions led by Franciscan friars to convert Indigenous communities to Christianity and anchor new settlements. But first, there was a problem to solve: Spain knew little about the rugged, uncharted territory north of Baja California. Before the empire could build its chain of missions and presidios, it had to send explorers to map the land and discover a reliable route into it.

On the advice of De Gálvez, the Viceroy of Mexico, Antonio Maria Bucareli y Ursua, approved a plan for an expedition, led by Antonio Maria Bucareli y Ursua, to explore the territory of Alta California. Followed to success of the first expedition in 1774, the Viceroy approved a second expedition to establish settlements.

Leadership and Major Figures

Several notable individuals played central roles in the De Anza Expeditions:

• Juan Bautista de Anza (1736 – 1788): A native of Sonora, New Spain (modern Mexico), De Anza was a seasoned frontier soldier and commander of the Presidio of Tubac (in present-day Arizona). He led two major expeditions from Sonora to Alta California — the first in 1774 (an exploratory mission to find a viable overland route), and the second in 1775–1776 (a colonizing expedition with settlers, soldiers, and families). De Anza’s leadership, diplomacy with Indigenous groups (especially the Yuma/Quechan at the Colorado River), and deep knowledge of desert travel were critical to the success of both journeys. His efforts directly enabled the founding of San Francisco’s presidio and mission and secured Spain’s northern frontier.
• Father Francisco Garcés (1738 – 1781): The mission chaplain was a Spanish Franciscan friar stationed at Mission San Xavier del Bac near Tucson, Garcés joined De Anza as the expedition’s spiritual leader and guide. Fluent in several Native languages and deeply familiar with the desert peoples, he served as a mediator and diplomat during encounters with tribes along the route, particularly the Yuma and Mojave. After the expeditions, Garcés continued missionary work among the Colorado River tribes until his death during the Yuma Revolt of 1781. His diaries remain an invaluable firsthand record of the landscape, Indigenous cultures, and the expedition’s hardships.
• Father Juan Díaz: A Franciscan friar, Díaz served as chief chaplain of the 1775–1776 expedition, overseeing the religious life of the colonists.
• Father Pedro Font: A Franciscan scholar and diarist, joined the expedietion as assistant chaplain. Font kept a detailed daily journal of the journey — describing landscapes, weather, encounters with Indigenous peoples, and the spiritual life of the colonists. His writings are one of the most valuable primary sources for historians studying the expedition.
• Lieutenant José Joaquín Moraga (1741 – 1785): A Spanish military officer born in Queretaro, New Spain (modern-day Mexico). Trained as a soldier in the frontier presidios of northern New Spain, Moraga became a trusted subordinate of Juan Bautista de Anza and joined the 1775–1776 colonizing expedition that established the first overland route from Sonora into Alta California. During the expedition, Moraga proved himself an able leader and organizer. When the group reached the San Francisco Bay area in 1776, De Anza returned south, leaving Moraga in command to carry out the next phase of colonization. In 1776, Moraga led the founding of the El Presidio Real de San Francisco and helped establish Mission San Francisco de Asís (Mission Dolores) with Father Francisco Palóu. He served as the first commandant of the San Francisco Presidio, making him effectively the founder of San Francisco as a Spanish colonial settlement. In 1777, he established El Pueblo de San José de Guadalupe, the first civilian settlement in California, to supply the presidio and mission.
• Sebastián Taraval: A Native of Baja California familiar with the routes of northern Baja and the desert corridor, acted as a guide and interpreter for both expeditions. His local knowledge was vital in navigating desert trails, finding water sources, and communicating with tribes along the way.

The De Anza expeditions were not the achievement of one man but of a network of explorers, priests, soldiers, settlers, and Indigenous allies who together bridged the deserts between Sonora and the Pacific Coast. Their combined efforts transformed Spain’s northern frontier, laying the groundwork for California’s mission era and the early growth of Spanish-Mexican society in the region.

The First Expedition: 1774 – Exploration

On January 8, 1774, Juan Bautista de Anza departed from Tubac (in what is now southern Arizona, then the Presidio of Tubac, in Sonora) with a small party of soldiers, servants, mules, horses and cattle to scout a viable overland route to the California coast.

The journey took them roughly 74 days to reach the coast (near the mission of San Gabriel Arcángel) and up to Monterey in Alta California, traversing deserts, mountain ranges, the Colorado and Gila rivers, and encountering Native American communities — especially the Yuma (Quechan) people at the Yuma Crossing of the Colorado River.

Key achievements of this reconnaissance trip included:

• Finding a workable land corridor from Sonora through Arizona into California (via Gila River corridor and Yuma Crossing).

• Establishing initial friendly relations (or at least workable passage) with indigenous groups along the route (especially the Yuma).

• Demonstrating that large‐scale travel with livestock was feasible (though still extremely arduous).

However, the expedition did not establish any large settlements; its purpose was route‐finding and reconnaissance. Having done that, the Spanish colonial authorities approved a more ambitious colonizing expedition, to bring settlers.

The Second Expedition: 1775-1776 – Settlement

Building on the success of the 1774 route survey, de Anza was charged with organizing a far larger expedition in 1775–76, aimed not only at reaching Alta California but colonizing it: bringing families, settlers, soldiers, livestock, and establishing new missions and presidios.

Composition and Departure

In October 1775 the expedition departed Tubac with some 240 colonists (soldiers, their families, servants, and children), plus hundreds of horses and mules, and a large herd of cattle.
The colonists were multi‐ethnic: European descent, native American origin, and Afro-Latino heritage; the expedition thus had a diversity of backgrounds.

The Journey

The route largely followed the corridor de Anza had scouted: along the Gila River, crossing the Colorado River at the Yuma Crossing, then westward through the Imperial Valley and the Colorado Desert (now part of the Anza‑Borrego Desert State Park) and into Southern California, and ultimately north toward Monterey and San Francisco Bay.

They arrived at Monterey in March 1776, and de Anza scouted further north to the San Francisco Bay area where a presidio and mission would be founded.

Challenges

The expedition faced severe hardships: desert terrain, scarce water, inclement weather (rain, mud, snow at mountain passes), dying livestock, and desertion among servants and soldiers.  Despite these obstacles, remarkably only one woman is recorded to have died (in childbirth) and four babies were born en route.

Accomplishments

• The expedition successfully opened a land corridor from Sonora into Alta California, enabling future settlement and supply overland.

• At the Bay Area, the site for the Presidio of San Francisco and the Mission San Francisco de Asís (Mission Dolores) was selected in 1776.

• The expedition enabled Spanish colonial authority to push further north into Alta California, and to extend the mission–presidio system into new territory.

The mission system itself (Franciscan friars) accompanied such expeditions or followed soon after: the missions were established to convert indigenous peoples and anchor Spanish cultural‐religious presence alongside military/presidio power. This intertwining of religious, military, colonial, and settler motives marks the period. As the National Park Service notes, the expedition’s goal was “to establish a mission and presidio on San Francisco Bay.”

Indigenous Interactions

The period of Spanish mission expansion in California (ca. 1769–1833) relied heavily on interactions with indigenous peoples. The expeditions led by de Anza encountered, negotiated with, or traversed lands of numerous native communities, including the Yuma/Quechan, the Pima (Akimel O’odham), and coastal groups (Ohlone in the San Francisco Bay area).

From the native point of view, the arrival of colonists and the founding of missions meant profound transformations: indigenous lands, economies, and lifestyles were disrupted as missions imposed agricultural labor and Spanish cultural norms. The overland expedition in effect made possible the extension of missions and presidios into regions previously not accessed by land.

It’s worth noting that de Anza’s success in securing hospitality or at least passage from some indigenous groups (e.g., Yuma at the crossing) was vital; without such cooperation the expedition likely would not have succeeded.

However, this relationship would turn sour in some places: for example, the trail would later be closed by a revolt of the Quechan (Yuma) in 1781, which cut off the land‐route for decades.

The Route

The route that de Anza pioneered covered roughly 1,200 miles (approx. 1,950 km) from Nogales/Tubac at the present day Mexico–Arizona border, through desert valleys, the Colorado River crossing, Imperial/Salton-type basins, then across Southern California into Monterey and north to San Francisco Bay.

The terrain ranged from Sonoran desert, mountain passes, river valleys, coastal foothills, marsh and bay areas. A particular challenge was water and livestock logistics in the desert segments such as the Borrego Valley and Imperial Valley (presently Anza-Borrego Desert State Park). The campsite El Vado in the Borrego Valley is a recognized landmark of the expedition.

By charting and establishing a trail across such varied landscapes, de Anza’s expedition transformed the geography of colonial California by linking interior New Spain to the Pacific coast via land, rather than purely relying on sea supply‐lines.

The Impact and Legacy

The de Anza expeditions brought not only soldiers and livestock but families and settlers who would become part of the early California citizenry (the Spanish/Mexican era settlers of Alta California). Many descendants of expedition families became prominent local leaders.

The overland connection helped Spanish colonial authorities to reinforce their claim to Alta California, enabling settlement and mission‐presidio expansion that formed the backbone of Spanish, then Mexican, California until the American era.

Mission System Expansion

With the route established, missions could be more easily supported, and the presidios could be supplied. Missions such as Mission San Francisco de Asís (1776) were placed in territory reached by de Anza’s expedition. The De Anza expeditions launched the mission period in California history, bringing conversion of indigenous peoples, the establishment of Spanish architectural and agricultural systems, and the creation of missions, pueblos, and ranchos.