Based on the timeline, what can be directly tied to the invention of the cotton gin?

A: industrialization in New England

B: economic hardship in the South

C: Spanish American war

D: the spread of slavery

The correct answer is D: the spread of slavery. The invention of the cotton gin by Eli Whitney in 1793 dramatically increased the efficiency of cotton production, which led to a significant increase in demand for cotton. This, in turn, caused a greater need for labor and ultimately resulted in an expansion of slavery in the United States.