I know very little about the taxation history of the United States after the revolution and am wondering what the first official tax, put on the people by the American government, actually was.
An article found here, entitled "The Estate Tax: Ninety Years and Counting" mentions the Stamp Tax of 1797, which is the earliest tax I can find post-revolution. It was enacted to raise funds "to defend the nation’s interests in response to an undeclared war with France that had begun in 1794". There may be earlier taxes enacted by the British government that simply continued but I can't find any reliable sources for that so it's purely speculation on my part.