Final answer:
John Marshall's service to the United States can best be described as him being the Chief Justice of the Supreme Court for almost 35 years. He played a crucial role in defining the modern court and establishing its power and role in the government. One of the most significant cases during his tenure was Marbury v. Madison.
Step-by-step explanation:
John Marshall's service to the United States can best be described as him being the Chief Justice of the Supreme Court for almost 35 years.
During his tenure, Marshall clarified the position of the Supreme Court and made it a central fixture in the process of government.
He is often credited with defining the modern court, clarifying its power, and strengthening its role.
One of the most important cases heard by the court during Marshall's tenure was Marbury v. Madison, which established the principle of judicial review.