Juan Bautista de Anza was Captain of the Royal Presidio at Tubac, Sonora (now Southern Arizona).  In 1774, he proved that an overland route to Alta California was possible by financing his own successful exploratory trip.  Planning to return with emigrants and a herd of livestock, he charted watering spots and pasturage and established contacts with native tribes along the route.

In 1775, the Viceroy of New Spain authorized Anza to command an expedition escorting soldiers (los soldados) and their families to occupy and settle the port of San Francisco.  Anza began to enlist volunteers in the large city of Cuiliacán, where poorer people might be likely to accept the rigors of an arduous trek to start a new life.  Recruits gathered at the Presidio of San Miguel de Horcasitas, Sornora's provincial capital.  Anza chose as his lieutenant José Joaquín Moraga.  Friar Pedro Font, a Franciscan missionary, was picked as expedition chaplain for his ability to read latitudes.

The final staging area was Tubac. Apaches had driven off the entire herd of 500 horses three weeks prior to the expedition's arrival, forcing it to continue with no fresh mounts.  Food supplies included six tons of flour, beans, cornmeal, sugar, and chocolate, loaded on and off of pack mules every day.  Materials from cooking kettles to iron for making horseshoes added more tonnage.  The commander and his servants had a tent, as did Padre Font and his assistants.  The families, cowboys, muleteers, and soldiers shared ten tents among them.

There were approximately 300 people, 340 horses, 165 pack mules and 302 cattle.  Over the next eighty days between Tubac and San Francisco, there was one death and three live births.  Thus, after enduring many trials and hardships, the colonizers finally arrived at their new home in California.  Juan Anza returned to Mexico City in 1776 to report on the  mission, where he learned he had been appointed commander of all the troops in Sonora.  He was later appointed governor of New Mexico by the King of Spain.

Anza successfully opened an overland route of emigration and supply from Sonora to the missions and settlements of Alta California.  He confirmed that San Francisco Bay was a great harbor.

The soldiers and families that Anza escorted brought with them their language, traditions, and diverse New World Hispanic culture.  The backgrounds of all soldiers and settlers were carefully recorded as español, mulato or mestizo. Almost all the expedition members were born on this continent and had mixed European, African or Indian parentage.  These influences changed the lives of the indigenous peoples and shaped the development of Arizona and California.