An income tax amendment to the Constitution was first proposed by Senator Norris Brown of Nebraska. He submitted two proposals, Senate Resolutions Nos. 25 and 39. The amendment proposal finally accepted was Senate Joint Resolution No. 40, introduced by Senator Nelson W. Aldrich of Rhode Island, the Senate majority leader and Finance Committee Chairman. The amendment was proposed as part of the congressional debate over the 1909 Payne–Aldrich Tariff Act; by proposing the amendment, Aldrich hoped to temporarily defuse progressive calls for the imposition of new taxes in the tariff act. Aldrich and other conservative leaders in Congress largely opposed the actual ratification of the amendment, but they believed that it had little chance of being ratified, as ratification required approval by three quarters of the state legislatures.

On July 12, 1909, the resolution proposing the Sixteenth Amendment was passed by the Congress and was submitted to the state legislatures. Support for the income tax was strongest in the western and southern states, while opposition was strongest in the northeastern states. Supporters of the income tax believed that it would be a much better method of gathering revenue than tariffs, which were the primary source of revenue at the time. From well before 1894, Democrats, Progressives, Populists and other left-oriented parties argued that tariffs disproportionately affected the poor, interfered with prices, were unpredictable, and were an intrinsically limited source of revenue. The South and the West tended to support income taxes because their residents were generally less prosperous, more agricultural and more sensitive to fluctuations in commodity prices. A sharp rise in the cost of living between 1897 and 1913 greatly increased support for the idea of income taxes, including in the urban Northeast. A growing number of Republicans also began supporting the idea, notably Theodore Roosevelt and the "Insurgent" Republicans (who would go on to form the Progressive Party). These Republicans were driven mainly by a fear of the increasingly large and sophisticated military forces of Japan, Britain and the European powers, their own imperial ambitions, and the perceived need to defend American merchant ships. Moreover, these progressive Republicans were convinced that central governments could play a positive role in national economies. A bigger government and a bigger military, they argued, required a correspondingly larger and steadier source of revenue to support it.

Opposition to the Sixteenth Amendment was led by establishment Republicans because of their close ties to wealthy industrialists, although not even they were uniformly opposed to the general idea of a permanent income tax. In 1910, New York Governor Charles Evans Hughes, shortly before becoming a Supreme Court Justice, spoke out against the income tax amendment. Hughes supported the idea of a federal income tax, but believed the words "from whatever source derived" in the proposed amendment implied that the federal government would have the power to tax state and municipal bonds. He believed this would excessively centralize governmental power and "would make it impossible for the state to keep any property".

Between 1909 and 1913, several conditions favored passage of the Sixteenth Amendment. Inflation was high and many blamed federal tariffs for the rising prices. The Republican Party was divided and weakened by the loss of Roosevelt and the Insurgents who joined the Progressive Party, a problem that blunted opposition even in the Northeast. In 1912, the Democrats won the presidency and control of both houses of Congress. The country was generally in a left-leaning mood, with a member of the Socialist Party winning a seat in the U.S. House in 1910 and the party's presidential candidate polling six percent of the popular vote in 1912.

Three advocates for a federal income tax ran in the presidential election of 1912. On February 25, 1913, Secretary of State Philander Knox proclaimed that the amendment had been ratified by three-fourths of the states and so had become part of the Constitution. The Revenue Act of 1913, which greatly lowered tariffs and implemented a federal income tax, was enacted shortly after the Sixteenth Amendment was ratified.

Instruction: Based on the following passage, give 3 reasons why the Sixteenth Amendment was passed and ratified.
Response: Reasons the Sixteenth Amendment to the US constitution was passed by Congress in 1909 and ratified by the states in 1913 include:
1. Democrats and progressives believed the income tax to be fairer method of generating revenue than tariffs (taxes on the import and export of goods).
2. Western and southern states were concerned about commodity prices, which were impacted by tariffs, and therefore preferred an alternative means of revenue.
3. Republicans were split on whether to oppose or support amendment.