America's declaration of independence from the British Empire was the nation's founding moment. But it was not inevitable.
Until the spring of 1776, most colonists believed that the British Empire provided them protection and opportunity. The mother country consumed colonists' goods, defended them from Native American Indian and European aggressors, and extended British rights to colonists. In return, colonists traded exclusively with Britain, obeyed British laws and customs, and pledged their loyalty to the British crown. For most of the eighteenth century, the relationship between Britain and her American colonies was mutually beneficial. Even as late as June 1775, Thomas Jefferson said that he would "rather be in dependence on Great Britain, properly limited, than on any nation on earth, or than on no nation."
But this favorable relationship began to decline in the wake of the Seven Years' War. In this conflict with France, Britain wracked up an enormous debt and looked to its American colonies to help pay for the war. Between 1756 and 1776, Parliament issued heavy taxes, including the Stamp Act of 1765 and the Tea Act of 1773. Unsurprisingly, Parliament's taxes met with stiff colonial resistance. But instead of compromising, Parliament passed oppressive measures to force colonists to obey the new laws. Eventually, tensions culminated in the shots fired between British troops and the colonial militia at Lexington and Concord in 1775.
Despite the outbreak of violence, the majority of colonists wanted to remain British. Only when King George III failed to address colonists' complaints against Parliament or entertain their appeals for compromise did colonists begin to consider independence as a last resort. In the spring of 1776, colonists still hoped for reconciliation with Britain. Those hopes were diminished, however, by the continuing war and rumors of a large-scale invasion of British troops and German mercenaries.
The first formal proposal for independence was not made in the Continental Congress until June 7, 1776. It came from the Virginian Richard Henry Lee, who suggested that "all political connection is, and ought to be, dissolved." But this was not a unanimous sentiment. Many delegates wanted to defer independence or avoid it outright. Still, Congress did nominate a drafting committee—the Committee of Five—to compose a declaration of independence. Thomas Jefferson, known for his eloquent writing style and reserved manner, became the principal author.
As he sat at his desk in a Philadelphia boarding house, Jefferson drafted a "common sense" treatise without, he claimed, opening a single book or pamphlet. Some of his language and many of his ideas drew from well-known political works, such as George Mason's Declaration of Rights and the new Virginia state constitution. But his ultimate goal was to express the unity of Americans—what he called an "expression of the American mind"—against the tyranny of Britain. 
Jefferson submitted his "rough draught" of the Declaration on June 28. Congress eventually accepted the document, but not without debating the draft for two days and making extensive changes. Jefferson was unhappy with many of the revisions—particularly the removal of the passage on the slave trade and the insertion of language less offensive to Britons. Benjamin Franklin tried to reassure Jefferson by telling him the now-famous tale of John Thompson, whose storefront sign bore the words: "John Thompson, Hatter, makes and sells hats for ready money." After a circle of critical friends offered their critiques, the sign merely read, "John Thompson" above a picture of a hat. 
Pressured by the news that a fleet of British troops lay off the coast of New York, Congress adopted the Declaration of Independence on July 4. The Congressional printer, John Dunlap, produced broadsides of the document to be distributed to the public. Weeks later, on July 19, Congress ordered an official copy of the Declaration; all 56 delegates of the Continental Congress signed it on August 2.
Throughout July and August, the Declaration was spread by word of mouth, delivered on horseback and by ship, read aloud before troops in the Continental Army, published in newspapers from Vermont to Georgia, and dispatched to Europe.Wherever it was heard or read, the Declaration roused support for the American Revolution and mobilized resistance against British tyranny.
1. Thomas Jefferson to John Randolph, August 25, 1775.
2."Richard Henry Lee Resolution of Independence," June 7, 1776.