Final answer:
The spread of slavery in North America was primarily due to the demand for labor on plantations growing cash crops like tobacco, indigo, and rice, with the Trans-Atlantic slave trade supplying the vast numbers of workers needed.
Step-by-step explanation:
The Primary Factor Contributing to the Spread of Slavery in North America
The spread of slavery in the colonization of North America was primarily due to the demand for labor brought about by the growth of plantation economies. Crops such as tobacco, indigo, and rice were labor-intensive and highly profitable in the trade networks of the time, leading to the vast importation of enslaved Africans. In the South, where these crops were predominant, the limited supply of indentured servants from Europe was insufficient, and so, slavery became the primary labor system, a concept that was very different from African labor systems. Unlike in Africa, slavery in the Americas was race-based, permanent, and hereditary - meaning children born to enslaved people also became slaves. This led to the establishment of a racial caste system that was integral to the economy of the Southern colonies.
Over time, the practice of slavery became deeply entrenched in the American economic system, especially with the advent of cotton as a major cash crop after the invention of the cotton gin. The unfathomable demand for labor to cultivate these crops led to the rise of the Trans-Atlantic slave trade, marking a dark period in human history. The North, with its more diverse economy, did not rely on slavery to the same degree and thus a regional and ideological divide formed, setting the stage for the Civil War.