What was the purpose of the Declaration of Independence

The introductory sentence states the Declaration's main purpose, to explain the colonists' right to revolution. In other words, “to declare the causes which impel them to the separation.” Congress had to prove the legitimacy of its cause. It had just defied the most powerful nation on Earth.

the tariff was created to protect industry in the northern part of the united states. industries in the north were being driven out of business by imported goods that were priced at a low rate. the goal was to protect these industries   by taxing the goods.