Mexico was the site of some of the earliest and most advanced civilizations in the western hemisphere. The Mayan culture, according to archaeological research, attained its greatest development about the 6th century AD. Another group, the Toltec, established an empire in the Valley of Mexico and developed a great civilization still evidenced by the ruins of magnificent buildings and monuments. The leading tribe, the Aztec, built great cities and developed an intricate social, political, and religious organization. Their civilization was highly developed, both intellectually and artistically. .
The first European explorer to visit Mexican territory was Francisco Fernández de Cordoba, who in 1517 discovered traces of the Maya in Yucatán. In 1535, some years after the fall of the Aztec capital, the basic form of colonial government in Mexico was instituted with the appointment of the first Spanish viceroy, Antonio de Mendoza. A distinguishing characteristic of colonial Mexico was the exploitation of the Native Americans. Although thousands of them were killed during the Spanish conquest, they continued to be the great majority of inhabitants of what was referred to as New Spain, speaking their own languages and retaining much of their native culture. Inevitably they became the laboring class. Their plight was the result of the 'encomienda' system, by which Spanish nobles, priests, and soldiers were granted not only large tracts of land but also jurisdiction over all Native American residents. .
A second characteristic of colonial Mexico was the position and power of the Roman Catholic church. Franciscan, Augustinian, Dominican, and Jesuit missionaries entered the country with the conquistadores. The Mexican church became enormously wealthy through gifts and bequests that could be held in perpetuity. Before 1859, when church holdings were nationalized, the church owned one-third of all property and land.