Who in America would benefit from new market? why?

New markets implied more money, hence more profits. Due to industrialization, America was manufacturing more than it was able to consume. Instead of letting the surplus to get wasted, the US felt it was wiser to invest and expand their market.

Explanation:

several states had passed similar laws, but they were limited to intrastate businesses. the sherman antitrust act was based on the constitutional power of congress to regulate interstate commerce.

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