Junípero Serra was a missionary who evangelised the territory in both California and Mexico.  As Puigdomènech explains in this work, the author aims to find "documentary evidence that certifies Sierra’s defence of the rights of the autochthonous people - contrary to what some people would have us believe-and his important humanitarian work aimed at improving precarious living conditions in the area".

De Petra en California: vida, pensamiento y legado de Junípero Serra reveals the sources of the education received by the founder of the missions to Mexico and California, incorporating the influence received from the doctrines of Saint Francis of Assisi and followers such as Saint Buenaventura, Ramón Llull and Duns Escoto. Added to this influence was a study, at the University of Majorca, of the great authors of the synthesis of the Greco-Roman philosophy and Christian theology- Saint Augustine and Saint Thomas Aquinas. He thus achieved a solid intellectual and doctrinal education which, along with his tireless missionary vocation, are the reflection of the personality of this Saint from Petra. 

The foundations and humanitarian work which the evangeliser carried out were the origin of the germ of an idea for cities such as San Diego, San Francisco or Los Angeles, among others, along the west coast of the United States of America.  It is for this reason that the Government of the United States decided to immortalise the figure of Junípero Serra in the Capitol in Washington.