In 1520 smallpox reached Tenochtitlan, the Mexica (Aztec) capital. Earlier that year its people had driven Hernán Cortés and his men out of the city. Now the disease killed huge numbers of them, including the new emperor, Cuitláhuac. When Cortés returned in 1521 with thousands of Tlaxcalan and other Native allies, he besieged a city already devastated by an epidemic. Tenochtitlan fell in August 1521.
That single event holds most of this topic: a biological exchange nobody planned, a conquest that depended on Native allies, and an empire built on the labor of the people it conquered.
What the Columbian Exchange was
The historian Alfred Crosby named it in 1972: the movement of plants, animals, people and diseases between the Americas and the rest of the world after 1492. It ran in both directions.
- To Europe, Africa and Asia: maize, potatoes, tomatoes and cacao. Maize and potatoes produced a lot of food per acre and helped Europe's population grow.
- To the Americas: wheat and sugar cane, and horses, cattle, pigs and sheep. Free-ranging livestock often ate or trampled Native fields.
- Disease: smallpox, measles and other Eurasian diseases met people who had never been exposed to them. Historians call these virgin soil epidemics.
How many people lived in the Americas in 1491 is still debated, and estimates vary widely. Historians agree that epidemics, worsened by war, forced labor and hunger, caused a catastrophic fall in Native populations.
Silver, ships and money
In 1545 enormous silver deposits were found at Potosí, in present-day Bolivia, and soon after in Mexico. At Potosí, a forced labor draft called the mita sent Indigenous men to work the mines, alongside many paid workers. The silver flowed into European and Asian trade, and the course links this mineral wealth to Europe's shift from feudalism toward capitalism.
Better ships made all of this possible. The Portuguese caravel, with its lateen sails, could handle long ocean voyages. Joint-stock companies, in which investors pooled money and shared risk, later funded English colonies.
Conquest
The Spanish did not conquer alone. Cortés depended on the Tlaxcalans and other enemies of the Mexica. Francisco Pizarro began the conquest of the Inca Empire in 1532 by capturing its ruler, Atahualpa, when the empire had just been through a civil war. Spanish officials read the Requerimiento (1513), in Spanish, demanding that Native peoples accept the authority of the Church and the Spanish monarchs or face war.
Native peoples resisted. In western Mexico the Caxcanes and their neighbors rose in the Mixtón War (1540–1542). Further north, Spain founded St. Augustine in Florida in 1565, and Juan de Oñate led colonists into New Mexico in 1598, where his forces attacked Acoma Pueblo the next year.
Labor, slavery and caste
The encomienda gave colonists the labor of Native people for farming and mining. In the Caribbean, the Taíno population collapsed under forced labor and disease. As Native workers died, the Spanish imported enslaved Africans, bought from European traders who partnered with some West African groups that practiced slavery.
The debate in Spain was real. Bartolomé de las Casas condemned Spanish cruelty, and Juan Ginés de Sepúlveda argued that Native peoples were naturally suited to conquest. The Crown's New Laws of 1542 banned enslaving Native people and limited the encomienda, but colonists resisted and the Crown softened them.
A caste system ranked everyone by ancestry: peninsulares (born in Spain) at the top, then criollos (Spanish ancestry, born in the Americas), then people of mixed ancestry such as mestizos, with Native and African people at the bottom.
Common mistakes students make
- Treating the exchange as one-way. American crops changed diets across Europe, Africa and Asia.
- Crediting conquest to Spanish weapons alone. Native allies and epidemics mattered at least as much.
- Giving one population figure as fact. Estimates for 1491 vary widely; say so.
- Mixing up peninsulares and criollos. Both had Spanish ancestry; birthplace set the rank.
Frequently asked questions
What was the Columbian Exchange in APUSH?
The transfer of plants, animals, people and diseases between the Americas and the rest of the world after 1492. It is Topic 1.4 in Period 1.
What were the effects of the Columbian Exchange?
New crops helped Europe's population grow, American silver fed European trade, and Eurasian diseases devastated Native populations.
Why did the Spanish switch to enslaved African labor?
Native workers died in huge numbers from disease and overwork, and the Crown restricted Native slavery, so colonists turned to the Atlantic slave trade.
What was the Spanish caste system?
A ranking of colonial society by ancestry and birthplace, with Spanish-born peninsulares at the top.
Try it
Say each answer before you flip the card. Then take one item from the exchange, such as the horse, silver or smallpox, and trace one effect it had on people in the Americas. What changed, and why then?
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