The act passed in 1765 that led to protests and was pivotal in the American Revolution was the Stamp Act. This legislation required colonists to purchase special stamped paper for documents, newspapers, and legal papers, imposing direct taxation without representation in Parliament. It ignited widespread opposition, leading to protests and the formation of groups like the Sons of Liberty. The unrest contributed to a growing revolutionary sentiment among the colonies, culminating in boycotts and ultimately the broader resistance that fueled the quest for independence.