How did industrialization impact the economy during the 1800s, and what role did slavery play in the United States before and during the Civil War?

Industrialization changed the United States a great deal, especially after the Civil War. Industrialization required interchangeable parts and mass production, and this took away from the work that skilled tradesmen received and put the work into the hands of unskilled factory workers.
Captains of industry such as Andrew Carnegie and John Rockefeller made enormous fortunes by using these unskilled laborers to create products cheaply. The rise of industrialization created huge gaps between the rich and poor, especially in America's cities. By 1900, America was looking for markets all over the world in order to have a place to sell its products. This also led to protectionist tariffs enacted by primarily Republican governments of the era that meant to protect industrialists' profits.  
Slavery created a small class of millionaires in the South as it took a great deal of money to buy slaves and maintain a plantation. By the time of the Civil War, the slaves in the South were worth more than the banking and railroad interests in the United States combined.
Of course, slavery also created a static social system in the South where it was impossible for one to become wealthy unless one was born into the planter class. Poor, lower-class white people resented the slaves for taking jobs they could have on the plantations. The lower classes would never have enough money to buy their own farms. The lack of opportunity caused by the static social system also led to fewer investment opportunities from the North and fewer immigrants willing to come South due to a lack of jobs compared with the North.
Slavery created social dilemmas for the nation that pledged that "all men were created equal." By 1850 it became the key campaign issue. During the war ending slavery would become a major cause for the North, especially with the Emancipation Proclamation.