Galván settled in San Antonio of Bexar early in the 1720s, about ten years after entering military service.
[1] He did well there, being promoted to alférez and later entrusted with 30 men on March 13, 1748, to protect the Mission San Xavier del Bac.
In the summer of 1749, Governor Pedro del Barrio Junco y Espriella went with Galván to investigate whether San Xavier could sustain a settlement.
In 1752, Spanish authorities approved an expedition to explore the Apache territory and locate a site for a possible mission.
[2] Galván was given charge of this expedition and set out the following year with a small group, including Father Miguel de Aranda, who worked at Mission Concepcion.