The United States Revenue Act of 1913, also known as the Underwood Tariff or Underwood-Simmons Act re-imposed the federal income tax and lowered the basic tariff rates from 40% to 25%, well below that of the Payne-Aldrich Tariff Act of 1909. The 1913 Act established the lowest rates since the Walker Tariff of 1857. Most schedules were put on an ad valorem basis (a % of the dollar value of the item.)
The duty on woolens went from 56% to 18.5%. Steel rails, raw wool, iron ore, and agricultural implements had zero rates.
The Act changed the duty for “Sporting, breech-loading double-barrel shotguns” to 15% ad valorem.

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