Final answer:
Enslaved Africans provided the primary workforce on plantations, performing arduous tasks under coercive conditions, essential for the production of cash crops such as sugar and cotton.
Step-by-step explanation:
The main source of labor on the plantations during the period of American slavery was enslaved African peoples. The labor was extremely hard and dangerous, especially on sugar plantations with large work gangs performing grueling tasks. Enslaved individuals were required to clear land, cultivate and harvest crops like sugar, coffee, rice, and cotton under harsh conditions, with the success of these plantations heavilydependent on the availability of this coerced workforce. African slaves weren't just used for manual labor; they were also skilled workers such as carpenters, blacksmiths, and seamstresses, with some developing skills that benefited both the slave and free Black populations. The domestic slave trade within the United States became a significant internal market after the international slave trade was outlawed in 1808, further bolstering the plantation system's dependency on African-American slave labor.