American Revolutionary groups that sprang up in Massachusetts and New York in 1765 to organize colonial opposition to the Stamp Act. In both colonies, serious riots, propaganda, and boycotts effectively nullified the measure. The organization then spread to other colonies and reactions to English “tyranny” were synchronized by committees of correspondence. Sons of Liberty were later responsible for the Boston Tea Party (1773), the radicalization of the Continental Congress (1774), and the tarring and feathering of pro-British loyalists.