History
The First Income Tax
National Museum of American History
The first Federal income tax was levied to help pay for the Union war effort. In the summer of 1861, Salmon P. Chase reported to the Congress that he would need $320 million over the next fiscal year to finance the war. He thought he could put his hands on $300 million by borrowing part of it and raising the rest through existing taxes and sale of public lands. He left it up to Congress to come up with a way to raise the remaining $20 million.
https://www.civilwar.org/learn/articles/first-income-tax
