The Boston Port Act was one of the Coercive Acts that Parliament passed in an effort to regain control of unruly Massachusetts on March 31, 1774.
The measure closed the port facilities in Boston effective June 1, 1774, until the city saw fit to reimburse the East India Company for the cost of the tea destroyed in the Boston Tea Party, and paid for the damage caused to the customs offices during the unrest. Bostonians were also required to prove to the crown's satisfaction that they were peaceable subjects.
Further, the Crown insisted on recognition from Massachusetts that duties such as the tea tax were properly within the purview of Parliament.
Lord North reasoned that the colonies would not "take fire" as a result of the Boston Port Act, since Boston was the only place punished. He was sorely mistaken. The American colonies recognized that the Port Act was just a prelude to the "Massacre of American Liberty. The colonies rallied to Boston's aid and the First Continental Congress was convened to direct opposition to the mother country.
See timeline of the American Revolution.