The Sons of Liberty was a secret organization of American patriots which originated in the Thirteen Colonies during the American Revolution. In 1767, the Sons of Liberty adopted a flag called the rebellious stripes flag with nine uneven vertical stripes (five red and four white). It is supposed that nine represented the number of colonies that were to attend the Stamp Act Congress. A flag having thirteen horizontal red and white stripes, used by American merchant ships during the war, became associated with the Sons of Liberty.