The cotton gin was invented in the 1700’s by Eli Whitney. The purpose of the machine was to separate cotton from seeds. Previously this job was extremely difficult and took a long time. With the cotton gin a single person could produce 50 times more cotton.
The effect of the cotton gin was that now farmers could plant more cotton and purchase more cotton gins, which would mean those farmers would need to purchase more slaves. The unintended effect of the cotton gin was an increase in slavery.