The Portuguese pioneered the transatlantic slave trade, beginning the practice in the 15th century and establishing a system that endured for over four centuries. This forced migration was central to the entire Portuguese colonial project, providing the labor that fueled its global economic expansion. Portugal transported an estimated 5.8 million enslaved Africans to the Americas, with the vast majority destined for its colony in Brazil. The use of enslaved labor was the foundation upon which the empire’s wealth and infrastructure were built.
Labor in Plantation Agriculture
The most extensive use of enslaved people was in large-scale, cash-crop agriculture, a system first tested on the Atlantic islands. The Portuguese established a plantation model on Madeira, São Tomé, and Cape Verde, using enslaved African labor to cultivate sugarcane in the 15th century. This template of monoculture, dependent on forced labor, was then expanded in Brazil starting in the 1530s.
The sugar economy in Brazil became the primary driver for importing millions of enslaved people, particularly to the northeastern captaincies of Pernambuco and Bahia. Enslaved workers performed the year-round labor required on the engenhos, or sugar mills, which were complex industrial operations. Tasks included planting and harvesting sugarcane, crushing the cane in the mills, and boiling the juice into crystallized sugar.
By the early 17th century, most of the colony’s approximately thirty thousand enslaved people worked on sugar plantations. This system resulted in high mortality rates due to the relentless pace of work and harsh conditions. Although the Portuguese Crown initially attempted to use enslaved Indigenous people, they quickly shifted almost exclusively to African labor, which was considered more practical for large-scale agriculture.
Mining and Resource Extraction
A significant shift in the use of enslaved labor occurred with the discovery of precious metals in the interior of Brazil during the late 17th century. The finding of gold in Minas Gerais, followed by diamonds, created a new economic cycle that rivaled the sugar industry. This discovery led to internal migration, with both Portuguese settlers and enslaved people moving from coastal plantations to the interior.
The mining boom required a new wave of imported enslaved people; an estimated 500,000 Africans were brought to the gold region alone. Enslaved miners were forced to pan for gold in riverbeds and dig in deep, unstable mines. The labor involved diverting rivers, digging up sediment, and sifting through tons of earth, often under the direct supervision of overseers.
The discovery of diamonds in the Serra do Frio region intensified the demand for specialized labor. The Crown implemented severe measures to prevent smuggling, creating a highly regulated environment where enslaved people were the primary workforce for extracting gemstones. This resource extraction was lucrative, with 800 metric tons of gold sent to Portugal in the 18th century, all extracted through forced labor.
The Urban and Domestic Workforce
Beyond the plantations and mines, enslaved people were a constant part of the urban landscape, both in the colonies and in the Portuguese metropole. Lisbon became a major center for the slave trade, and by the mid-16th century, people of African descent, both enslaved and free, made up about ten percent of the city’s population. Enslaved individuals in cities like Lisbon, Salvador, and Goa performed a wide variety of domestic and skilled labor roles.
Domestic service was a common role, with enslaved women and men working in wealthy homes as cooks, cleaners, and childcare providers. Enslaved people also provided essential unskilled labor that kept colonial cities functioning. This included working as porters, dockworkers unloading ships, and laborers in construction, such as rebuilding Lisbon after the 1755 earthquake.
Many enslaved people in urban centers engaged in skilled trades or worked as “slaves of gain.” They were hired out by their owners or allowed to earn money as street vendors. This urban labor was integral to the daily life and economy of the Portuguese empire, underscoring the dependence on forced labor even far from the colonial plantations.
The Foundation of Colonial Outposts and Trade
The initial phase of Portuguese expansion relied on enslaved labor to establish the physical infrastructure of the empire. On previously uninhabited islands like Cape Verde and São Tomé, enslaved Africans were used to clear land, build fortifications, and establish the first settlements. This foundational labor was necessary to transform these strategic outposts into viable colonies and trading hubs.
Enslaved people were also a primary commodity in the Portuguese trade network, generating profit through their sale and transport. The Portuguese established trading posts, or feitorias, along the African coast, such as Elmina, which were central to human trafficking. These posts served as collection points where enslaved people were acquired from African traders in exchange for European goods.
The Portuguese also acted as major suppliers of enslaved people to other European powers, including the Spanish colonies in the Americas. The transport of millions of people across the Atlantic, known as the Middle Passage, was a lucrative enterprise that formed a cornerstone of the empire’s finances. The entire system of colonial expansion was built on the dual use of enslaved people: as a source of labor for production and as a valuable, tradable commodity.