Why were monopolies formed? Why did the government then have to create antitrust legislation?

Explanation:

The Sherman Antitrust Act is a law the U.S. Congress passed to prohibit trusts, monopolies, and cartels.Its purpose was to promote economic fairness and competitiveness and to regulate interstate commerce.Ohio Sen. John Sherman proposed and passed it in 1890.

the answer to your question is a. the salt plains

in 1811, he led an expedition, known as the george c. sibley expedition, to improve relations with the pawnee and kansa tribes, and also to locate the rumored jefferson's salt mountain