John Steele Gordon provides a helpful survey of the history of American taxation, here, including the chronically avoided topic of how the tax on corporate profits (ruled constitutional as an excise tax "on the privilege of doing business as a corporation") was meant to be a temporary tax on the rich:
In the first decade of the 20th century, the stock of corporations was owned almost entirely by the rich. So taxing corporate profits was, in a very real sense, taxing the rich. Congress passed the legislation and in 1911 the Supreme Court ruled unanimously that the tax was constitutional. ...
Unfortunately, the [subsequent] personal income tax did not replace the corporate income tax that had originally been intended only as a stopgap. Nor did Congress integrate the two taxes so that income, whether corporate or personal, was only taxed once. The two taxes simply ignore each other as if corporations are owned by Martians, not people.
At the tax levels of the early 20th century, the harm was inconsequential. But when tax levels rose dramatically to fund the great wars that soon followed the personal income tax, the pressure to legally avoid taxes rose equally. As a result, the two separate, uncoordinated tax systems became a uniquely powerful engine of complexity as accountants and lawyers have played the two systems off each other and Congress has tried, unsuccessfully, to close or regulate the resulting “loopholes.” ...
The two income taxes have been the main reason that the tax code has exploded to a 4-million-word incomprehensible mess.
