Answer:
The answer to the question: How did horizontal integration change the way business was done in America, would be: it was the way that big tycoons, like Rockefeller, took out the competition and the mega empires, or conglomerates of one industry were born. It changed the way business was done in America, especially in the oil industry because when someone had to deal with that industry, they would always have to deal with the same company, and there were no options. Competition was eliminated.
Step-by-step explanation:
Horizontal integration is a concept that was born with John Rockefeller and his oil companies. Deciding that he did not want to have competition, but be one enormous corporation, Rockefeller began to outbuy all the competitors inside the oil industry, and thus, he became the sole owner of the entire process of oil production, from extraction, to shipping, to selling. This type of move, later became known as monopoly, and some other millionaires of the likes of Rockefeller did similar things as he did, but Rockefeller is the best example of horizontal integration.