Some historians support the idea that his mother was the slave of a canon, and that later she married a soldier of Spanish origin who set up a grocery store with which he paid for his stepson's law degree.
[1] As an adult, his political enemies sought to discriminate against him using the criteria established in the Spanish colonies by the Statutes of blood cleansing, maintaining that his mother descended from indigenous or African slaves and applying the qualifiers "zambo" or "mulatto" .
[2] He was the only survivor of eleven children and spent his childhood in relative economic scarcity: when he died, after spending his fortune helping his son, his father owned a grocery store and a slave.
That same year, when the French invasion of Napoleon bonaparte to Spain became known, Monteagudo wrote a play entitled Dialogue between Atahualpa and Fernando VII.
In January 1818 he wrote the Proclamation of the Independence of Chile (the writing was disputed with Miguel de Zañartu), and he became a confidant and advisor to the director Bernardo O'Higgins, also a member of the Lautaro Lodge.
After the patriot victory in the Battle of Maipú, he was involved in the summary execution of the brothers Juan José and Luis Carrera, and probably also in the murder of Manuel Rodríguez Erdoíza, after being detained by O'Higgins.
[11] In 1821 Monteagudo joined the liberating expedition under the command of San Martín as auditor of the Argentine army in Peru, replacing the recently deceased Antonio Álvarez Jonte.
His first success was to convince the governor of Trujillo to go over to the patriots: he was the Marquis of Torre Tagle, future first Peruvian president (with the title of Supreme Delegate) of Peru.
Tagle had entrusted his fate to the patriot governor José María Carreño, who in turn placed him in the custody of Lieutenant Colonel Francisco Burdett O'Connor, then Panama's chief of staff, with whom he established a friendly relationship.
[18] Despite the validity of the legislative resolution that ordered the ban, Monteagudo returned to Peru through Trujillo and accompanied Bolívar with the rank of colonel in the final campaign of the Peruvian War of Independence.