The Sons of Liberty organized in Boston Massachusetts to protest the Stamp Act of 1765. The idea quickly spread across the other colonies (via Twitter?) and in 1767 they adopted a flag design of 9 vertical stripes, 5 red and four white to represent the nine protesting colonies. By 1776 all 13 colonies had joined the fight for independence so this 13 stripe version became popular.
The Grand Union Flag is considered to be the first national flag of the United States. It added the British Flag to the canton (upper left corner) of the Sons of Liberty flag. The flag was first flown on the USS Alfred in Philadelphia on December 3, 1775 by Lieutenant John Paul Jones. It was used by American Forces through early 1777.
On June 14, 1777, the Continental Congress passed the Flag Resolution stating: “Resolved that the flag of the thirteen united states be thirteen stripes, alternate red and white, that the union be thirteen stars, white in a blue field, representing a new constellation.” This was our first “Stars and Stripes” flag.
An almost square version of the flag was flown by General George Washington during his winter encampment at Valley Forge. It used the arrangement of the five pointed stars of the Stars and Stripes, 3, 2, 3, 2, 3 array, for its six pointed stars. It symbolized the presence and authority of Washington as Commander in Chief.
The Gadsden Flag had its roots in a Benjamin Franklin image of a serpent cut in pieces with the segments labeled with abbreviations of the names of the colonies. It was calling for unity in opposing the French on the western frontier of the thirteen colonies. Paul Revere joined the snake’s pieces in the Massachusetts Spy, or Thomas’s Boston Journal in 1774. In 1775, some Marines boarding the USS Alfred carried drums painted in yellow with the American rattlesnake (unique in the world to our continent) with 13 rattles and the motto “Don’t Tread on Me.” Christopher Gadsden of South Caroline Sons of Liberty was on the congressional navy committee. Gadsden made the first yellow field “Don’t Tread on Me” flag and presented one to the SC state legislature and one to the first commander in chief of the US Navy, Rhode Islander Esek Hopkins.
Commodore Hopkins devised the Navy Jack combining the thirteen stripe background and the Gadsden theme.
The Culpeper Virginia militia made their flag with a version of the same theme and the “Liberty or Death” motto which Governor Patrick Henry took from his sisters and the Fincastle Resolutions.
Link to some patriot flag history