For America250, the 1776 pamphlet that helped popularize independence was Common Sense.
Thomas Paine published Common Sense anonymously in Philadelphia on January 10, 1776. Written in accessible language, it attacked hereditary monarchy and argued that the American colonies should seek complete independence from Great Britain rather than reconciliation.
The pamphlet reached readers through inexpensive printed editions and public readings. Its direct style made complicated political arguments understandable to a broad audience. It appeared months before Congress formally declared independence and helped make separation a subject of open popular debate.
Common Sense is not the same work as Paine’s The American Crisis, which began publication in December 1776 after the Declaration and was intended to strengthen Revolutionary morale. The Federalist Papers came later, in 1787 and 1788, during the debate over ratifying the Constitution.