Final answer:
The most successful component of John Adams's presidency was the appointment of Chief Justice John Marshall, which significantly influenced American law and government for decades.
Step-by-step explanation:
One of the most successful components of John Adams's presidency, despite the tumultuous times, was his appointment of Chief Justice John Marshall. Adams's exit from the presidency was mingled with controversy particularly around the judiciary, but this appointment proved to be his most enduring legacy.
Marshall's tenure on the Supreme Court shaped American law and government for decades, establishing the principle of judicial review and strengthening the role of the federal government in the United States.
In the context of a young nation still finding its footing, this appointment was crucial for the development of the American legal system and provided a strong and consistent interpretation of the Constitution that would guide the country for years to come.