It was an economic change because when Eli Whitney created the Cotton Gin it made cotton in demand because they were producing it quicker.
The cotton gin was the most economic difference because the cotton had more demand and when it was invented more slaves has to be bought.
How it affect the country is that it made the south the cotton producing part of the country.
Eli Whitney - Invented the Cotton Gin
Evidence 1: "The South became the cotton producing part of the country because Whitney’s cotton gin was able to successfully pull out the seeds from the cotton bolls."
Source 1: http://score.rims.k12.ca.us/score_lessons/cotton_gin/pages/reading.html
Evidence 2: "Demand was fueled by other inventions of the Industrial Revolution, such as the machines to spin and weave it and the steamboat to transport it."
Source 2: http://www.eliwhitney.org/7/museum/eli-whitney/cotton-gin
Evidence 3: "While it was true that the cotton gin reduced the labor of removing seeds, it did not reduce the need for slaves to grow and pick the cotton. In fact, the opposite occurred. Cotton growing became so profitable for the planters that it greatly increased their demand for both land and slave labor."
Source 3: https://www.archives.gov/education/lessons/cotton-gin-patent
Evidence 4: Finally, tobacco growing moved westward, taking slavery with it.
Source 4: http://www.let.rug.nl/usa/outlines/history-1990/westward-expansion-and-regional-differences/cotton-promotes-slavery.php
Black slaves working Cotton Gin
The modern mechanical cotton gin was invented in the United States of America in 1793 by Eli Whitney (1765–1825). Whitney applied for a patent on October 28, 1793; the patent was granted on March 14, 1794, but was not validated until 1807.
When it was invented the south was more effected by this then the north because it had slaves and the south were the slave states.
It affect the westward expansion by having the slaves grow tobacco and then move west.
What else was going on at the time? Trains and steamboats were invented.