The last of the measures inaugurating the new colonial system sparked the greatest organized resistance. Known as the "Stamp Act," it provided that revenue stamps be affixed to all newspapers, broadsides, pamphlets, licenses, leases or other legal documents, the revenue (collected by American customs agents) to be used for "defending, protecting and securing" the colonies.
The Stamp Act bore equally on people who did any kind of business. Thus it aroused the hostility of the most powerful and articulate groups in the American population: journalists, lawyers, clergymen, merchants and businessmen, North and South, East and West. Soon leading merchants organized for resistance and formed non-importation associations.
Trade with the mother country fell off sharply in the summer of 1765, as prominent men organized themselves into the "Sons of Liberty" -- secret organizations formed to protest the Stamp Act, often through violent means. From Massachusetts to South Carolina, the act was nullified, and mobs, forcing luckless customs agents to resign their offices, destroyed the hated stamps.
Spurred by delegate Patrick Henry, the Virginia House of Burgesses passed a set of resolutions in May denouncing taxation without representation as a threat to colonial liberties. The House of Burgesses declared that Virginians had the rights of Englishmen, and hence could be taxed only by their own representatives. On June 8, the Massachusetts Assembly invited all the colonies to appoint delegates to the so-called Stamp Act Congress in New York, held in October 1765, to consider appeals for relief from the king and Parliament. Twenty-seven representatives from nine colonies seized the opportunity to mobilize colonial opinion against parliamentary interference in American affairs. After much debate, the congress adopted a set of resolutions asserting that "no taxes ever have been or can be constitutionally imposed on them, but by their respective legislatures," and that the Stamp Act had a "manifest tendency to subvert the rights and liberties of the colonists."
Source: U.S. Department of State