Final answer:
In Munn v. Illinois, the Supreme Court ruled that privately owned grain elevators were subject to government regulation, supporting the Grange's efforts to protect farmers.
Step-by-step explanation:
In the Supreme Court case of Munn v. Illinois, the court ruled that privately owned grain elevators were operated in the public interest and subject to government regulation, similar to utility companies. This case was significant as it supported the Grange's efforts to regulate monopolistic practices and protect the interests of farmers.