Final answer:
The Sixteenth Amendment's ratification allowed the Federal government to impose an income tax on both individuals and corporations, introducing a system of progressive taxation and ensuring a steady revenue source for the government.
Step-by-step explanation:
The ratification of the Sixteenth Amendment to the U.S. Constitution was necessary to validate the Federal income tax on corporations. The ratification of the Sixteenth Amendment was necessary for the Federal government to impose an income tax, not specifically just on corporations, but on individuals as well. This amendment came about after the Supreme Court declared earlier federal income tax laws unconstitutional, leading Congress to pass the amendment to clearly authorize such a tax within the Constitution. The Sixteenth Amendment was ratified in 1913 and allows Congress to levy a tax on incomes, from whatever source derived, without apportionment among the states and without regard to any census or enumeration. This provided a steady stream of revenue for federal expenses, reducing reliance on tariffs and introducing a system where those with higher incomes would face higher tax rates, a structure known as progressive taxation.