Around 1750, the British mainland American colonies had a population of approximately 1.5 million. In addition to settlers from Great Britain, a steady stream of German immigrants began to arrive in the late 1600s and reached its peak between 1749 and 1754, when more than 5,000 Germans arrived annually. Each year 3,500 black captives arrived from Africa or the Caribbean. Nearly 1 in 5 Americans, or 300,000 people, were enslaved. Poverty in Northern Ireland forced a massive flight of Scots-Irish to the colonies.
I think the mexican war where we took land from the mexico or the illiouisiana purchase
The correct answer is increase in industrialization.
Due to the technological advancements of the mid-late 1800's, Americans started to rely more on industry rather than farming. Working in a factory rather than a farm had its perks. People who worked in a factory had guaranteed wages, whereas in farming the amount of money a person makes is dependent on several different factors like the amount of people who want to buy your products, climate, location, etc.
