The act that closed the Boston Harbor as a response to the Boston Tea Party was the Boston Port Act, part of the Coercive Acts (also known as the Intolerable Acts) passed by the British Parliament in 1774. This act aimed to punish the Massachusetts colonists for the Boston Tea Party, where colonists protested against British taxation by dumping tea into the harbor. The closure of the harbor significantly harmed the local economy and fueled further resentment toward British rule, uniting the colonies against perceived tyranny and contributing to the growing revolutionary sentiment that led to the American Revolution.