Horrified by indigenous religious traditions of human sacrifice and polytheism, the Roman Catholic colonizers quickly revealed their plans of renouncing Aztec and other religions in trade for their own traditions. “Extreme” practices such as human sacrifice were used by colonizing forces as more reason to assimilate and eliminate native peoples. While human sacrifice and other rituals were a form of resistance for some time, the conquest of the area by the Spanish was too strong, and the rituals died out of common practice. There were battles between the colonizers and indigenous peoples over the use of pre-existing temples for religious use, with some concessions made on each side in rare occasions, such as Spanish friars telling other colonizers to remove themselves from the spaces and indigenous leaders conceding some spaces to the Spanish to keep peace and some being credited with the first calls against slavery and for independence. However, this was relatively uncommon, and colonizing power overruled in a majority of scenarios. Later, where temples had once stood, churches were built on the same land. Other Indigenous religious symbols were also replaced, such as statues, art, and artifacts. Conquistador Hernán Cortés wrote, “The most important of these [religious] idols, and the ones in whom they have the most faith, I had taken from their places and thrown down the steps.”

Following the conquering of Tenochtitlan in 1521, the indigenous peoples were forcefully converted at incredible rates. Native leaders and children were the subject of efforts for conversion, as they were either the most influential to the indigenous community or likely to carry it on to the next generation. Native children were kidnapped as part of conversion efforts, and resistance by native leaders was met with the threat of death or murder itself. It is also important to note that as in many colonial contexts, some native elites were turned into allies for the conquistadors and aided in the triumph of colonial power; however, these elites are not to fully be blamed, as they too are products of the colonial system.

A group called the Twelve Apostles of Mexico arrived in 1524, one of the first groups to arrive with their sole purpose being conversion. To break down the daunting task of converting the entire local population, there were specific locations of conversion. Larger towns used to convert people were called doctrinas, and smaller areas, visited only incrementally, were called visitas. Hospitals were also created to be main conversion sites. In 1540, the first convent was built.  

Because the native population did not speak Spanish and efforts to convert were dependent on a similar language, Spanish friars and other leaders utilized bilingual dictionaries, books of psalms, etc. to communicate with those who spoke Nahuatl. To enforce and convert Roman Catholicism, the Holy Office of the Inquisition was formed in 1569, and in 1572, the first Jesuits arrived in Mexico. The Catholic church kept records of life events, such as birth, death, and marriage for an extended amount of time.

Mexico’s first constitution stated that it would be a Roman Catholic country by law, and the government took all property of the church into its possession. Discussion over the religion’s influence on the state became increasingly complicated as it was being decided what form of government to institute. By the mid-1850s, there were people who were strongly secular and calling for the state to be disconnected from the church, called anticlericalists. The removal of dictator Antionio López de Santa Anna in 1854 with the Plan of Ayutla sparked La Reforma (1855-1863) under leader Benito Juárez, which worked to get rid of any privileges religious and military leaders still held. Three years after his arrival, Maximilian of Hapsburg (emperor of Mexico) was killed in 1867, and what followed was a “series of anticlerical governments.” In this same time frame, the French came to occupy Mexico City and claimed rulership.