Final answer:
The first U.S. federal income tax was enacted during the Civil War, not the Spanish-American War, with relatively modest rates for the wealthy. The 16th Amendment provides Congress the power to tax income, and income tax was once deemed unconstitutional, leading to the amendment's adoption.
Step-by-step explanation:
The history of the U.S. personal income tax is both complex and integral to understanding government funding. Contrary to the first statement, the first federal income tax was established during the Civil War, not for the Spanish-American War. Addressing the second claim, initially, the marginal tax rate was not very high; it targeted mainly the wealthy with progressive rates but started at only 1% and rose to a maximum of 7%. The 16th Amendment, as correctly mentioned in the third statement, expressly granted Congress the power to levy an income tax without apportioning it among the states based on population. Lastly, early incarnations of income tax were indeed ruled unconstitutional, which led to the adoption of the 16th Amendment to settle the issue and introduce the income tax in a constitutionally sound manner.