The tax was intended to pay for the military defense of the colonies, which had become more costly in the wake of the French and Indian Wars and the Seven Years War in Europe.
The amount of the tax ranged from three pence to six pounds on a few items. Six pounds is roughly equivalent to $10 today, but at the time it was several months' income for many people.
This tax led to outrage on the part of Americans greater than any act of the British government up to that time. The colonial governments and citizens began to organize and protest "taxation without representation," which was contrary to English common law. Violent protests also occurred in some cities.
The tax was never effectively collected. It was repealed less than five month later. But the organizations and the spirit of resistance that it engendered remained, leading eventually to the much more famous Boston Tea Party and the shot heard round the world.

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- Jim