By the end of the 15th century, the Middle Ages came to a close as the modern world emerged. The legacy of the Middle Ages, the "Age of Faith," left its mark on the future of religion in Europe and after 1492, on the Americas. That year, Spain militarily defeated the Moors and initiated a period of expulsion for those who would not convert to Christianity. Following Columbus' first voyage, Spain had a new goal in that regard. When the cartographer Juan de la Cosa drew the first map of the Americas in 1500, he depicted a symbol of the Medieval past on the extreme left of his map where he had placed the North American coastline -- St. Christopher bearing the Christ child across the sea. In his Book of Prophecies (1501), a collection of biblical texts presented to Spain's sovereigns, Christopher Columbus, who signed his name Cristo Ferens, or Christ Bearer, asserted that the first steps toward bearing Christianity across the Atlantic had been taken.
Symbolically, just as Saint Christopher had carried the Christ child across a raging river, Spain was poised to send missionaries to Christianize the New World. In the papal bull of 1508, Universalis Ecclesiae (Of the Universal Church), Pope Julius II declared that the king of Spain would be the head of the Church in Spain and its empire. Such an empowerment clearly meant that along with Spanish law, governance, language, and culture, the Roman Catholic religion, too, would cross from Europe to the Americas and that the king of Spain would engage in the spread of Christianity to the native peoples of the New World. His charge would be to establish missions throughout the Western Hemisphere and, later, the Philippines. Thus began the history of the missions that across time would become a part of our national story and influence our shared common history with Spain, Mexico and Latin America.
Throughout the colonial period, the missions Spain established would serve several objectives. The first would be to convert natives to Christianity. The second would be to pacify the areas for colonial purposes. A third objective was to acculturate the natives to Spanish cultural norms so that they could move from mission status to parish status as full members of the congregation. Mission status made participating natives wards of the State instead of citizens of the empire. Aside from spiritual conquest through religious conversion, Spain hoped to pacify areas that held extractable natural resources such as iron, tin, copper, salt, silver, gold, hardwoods, tar and other such resources, which could then be exploited by investors. The missionaries hoped to create a utopian society in the wilderness.
To assure that the missionaries would be able to sustain themselves, the king of Spain established the Patronato Real de las Indias (Royal Patronage of the Indies) which supported the Spanish Crown's absolute control over ecclesiastical matters within the empire. The Spanish king and his council approved missionaries to go to the Americas, directed the geographic location of missions and allocated funds for each projected enterprise. Under the Patronato Real, which also governed appointments of Church officials to high office, some viceroys in Mexico and Peru were also archbishops, further cementing the Church-State alliance in a common cause. The missions served as agencies of the Church and State to spread the faith to natives and also to pacify them for the State's aims. By intermingling religion, politics and economics, the Patronato Real formed a large archival record of exploration, settlement, missionary activity, ethnographic data, and extraction of raw resources.
In North America, early missionary efforts commenced in places known as La Florida (after 1565 and along the eastern coastline to Chesapeake Bay by the early 1570s), Nuevo México (after 1598), Texas (along the Río Grande, late 1690s), Pimería Alta (present southern Arizona and northern Sonora--1680s) and, lastly California (1770s). Far from Spanish settlements, lone missionaries lived and worked at great peril among mostly hostile natives. Generally avoiding Great Plains and mountain tribes with strong warrior castes, missionaries focused their efforts on sedentary farming tribes, such as the Pueblos of New Mexico and semi-sedentary tribes along river ways in Texas and Arizona.
In most cases, Spanish arms were necessary for the mission program to succeed, especially in northern New Spain, today's Greater Southwest and northern Mexico. Tierra de guerra (Land of War) were noted on Spanish maps as Apachería, Comanchería, Centro de Navajo, Tierra de los Yutas, and others. Where possible, presidios (forts) were constructed near settlements and missions. In 1772, Friar Romualdo Cartagena, guardian of the College of Santa Cruz de Querétaro, one of the training centers for missionaries, wrote;
What gives the missions their permanency is the aid which they receive from the Catholic arms. Without them pueblos are frequently abandoned, and ministers are murdered.... It is seen every day that in missions where there are no soldiers there is no success.... Soldiers are necessary to defend the Indian from the enemy, and to keep an eye on the mission Indians, now to encourage them, now to carry news to the nearest presidio in case of trouble. For the spiritual and temporal progress of the missions two soldiers are needed...especially in new conversions. 
The role of the State was ever-present in the evolution of the missions throughout the Americas.
Theoretically, the missions were designed for a ten-year period, after which the missionaries were expected to move on to newly established areas. The scheduled plan of conversion did not work well due to Indian resistance to the rigors of the missions. In the long run, arguing that the natives were imperfectly converted because they reverted to their spiritual ways in secret, friars proposed that missions be extended another decade. Often such extensions lasted for several decades, if not a century, longer than intended.
By the end of the eighteenth century, and especially after the Latin America's Independence Movement from Spain, newly established revolutionary governments removed mission lands from Church authority. In most cases, emerging Western Hemispheric nations granted citizenship to native groups, kept them as wards of the state, or treated them as social outcasts.
Spanish colonial missions in North America are significant because so many were established and they had lasting effects on the cultural landscape. Their legacy is firmly a part of our national story and patrimony, and it highlights the common heritage the United States shares with Spain, Mexico and Latin America. Spain was not alone in missionary enterprises throughout the New World. French and Portuguese missionaries also made inroads in Canada, Brazil, and other parts of the Americas. To them, the mission served similar purposes: the spiritual conversion of natives and the pacification of precarious colonial frontiers for settlement, European economic exploitation, and development. Other nations employed the same methods in remote areas such as places in India, Africa, and Australia. The Spanish missions, like forts and towns, were frontier institutions that pioneered European colonial claims and sovereignty in North America.
Much has been written about the missions and their legacy ranging from the diffusion of Spanish culture, religion, governance, language, etc. to dialogues condemning their role in altering native cultural practices, customs and spiritual beliefs. No doubt a cultural fusion resulted from European and native contact, and many tribes that participated in the evolving mission process still practice Catholicism. While colonists intended to convert, civilize and exploit native groups, the natives had their own notions about being exploited, or having their cultural and spiritual domains threatened by catastrophic colonial policies imposed on them. Their view, far from the utopian dreams of the missionaries, was often expressed as an unequivocal rejection of the mission process. Native American resentment toward the missions and overall colonial policies often resulted in a series of rebellions that sometime took years, if not decades, to resolve. Over time, the missions made their mark on American Indian tribes, and Indian spiritual customs, in part, melded with Christianity.
The Spanish missions featured in this travel itinerary are windows to our national past. As such, visitors to them learn that history is not as absolute as it appears in textbooks. Seeing the Spanish missions is to experience a history that reminds us that the human experience is relative to the cultural values of a different time, people, traditions, and language. Beyond the splendor of the architecture of the missions, what we see today is the cumulative effect of a historic process Spain triggered with its efforts to govern and Christianize the New World, thereby culturally changing the land and people forever.
 John Francis Bannon, editor, Bolton and the Spanish Borderlands (1964), pp. 201-202.