In 1814 he crossed the Andes with many Chilean patriots and met General José de San Martín; they became friends and collaborators.

In 1815, Santa María de Oro was elected by San Juan to the Congress of Tucumán and served in 1816 for the declaration.

He was firmly in favour of a republic and opposed those who wanted a constitutional monarchy, also believing that the people should decide.

Santa María de Oro returned to San Juan and then to Chile where he was appointed Provincial superior of his order.

Santa María de Oro was a second cousin to Domingo Sarmiento, President of Argentina between 1868 and 1874.