John Adams built a successful legal practice in Massachusetts and entered public controversy through essays opposing British imperial policies. In 1770 he defended soldiers accused after the Boston Massacre, upholding their right to representation. As a Massachusetts delegate to the Continental Congress from 1774, he advocated of independence. He nominated George Washington to command the Continental Army and served on the committee preparing the Declaration of Independence in 1776.

Adams undertook diplomatic service in Europe during the Revolutionary War, seeking recognition, loans, and commercial agreements. He secured Dutch recognition and financial assistance and joined Benjamin Franklin and John Jay in negotiating the peace with Britain, concluded in 1783. During a return home he drafted much of the Massachusetts Constitution of 1780. His writings on government emphasized divided powers and safeguards against the domination of public affairs by any single social group. In 1785 he became the first United States minister to Britain.

Returning home, Adams served as vice president under Washington from 1789 to 1797. Elected president in 1796, he inherited deteriorating relations with France and intense partisan conflict. The XYZ Affair, involving demands made to American envoys, increased pressure for war. His administration expanded the navy and conducted the undeclared naval conflict known as the Quasi-War. Adams nevertheless reopened negotiations, obtaining a settlement in 1800. His decision to pursue peace alienated Federalists who favored a harder line, including Alexander Hamilton.

Adams signed the Alien and Sedition Acts in 1798. The legislation increased restrictions on immigrants and enabled prosecutions of political critics, provoking serious challenges to freedom of expression. He also faced resistance to federal taxation and pardoned leaders convicted following Fries's Rebellion. Divisions within his party and opposition from Jefferson's supporters contributed to his defeat in the election of 1800. He left office in 1801 as national power passed to a rival political party.

In retirement Adams wrote extensively and eventually renewed his correspondence with Thomas Jefferson. Their letters explored revolution, religion, political institutions, and the meaning of their shared public experience. He died on July 4, 1826, the same day as Jefferson. His career linked independence and diplomatic recognition to the pressures of republican government.