Tariff
A tariff is called an optimal tariff if it's set to maximize the welfare of the country imposing the tariff. It is a tariff derived by the intersection between the "trade indifference curve" of that country and the offer curve of another country. In this case, the welfare of the other country grows worse simultaneously, thus the policy is a kind of "beggar thy neighbor policy". If the offer curve of the other country is a line through the origin point, the original country is in the "condition of a small country", so any tariff worsens the welfare of the original country.
Tariff in United States history
Henry Clay and his Whig Party, envisioning a rapid modernization based on highly productive factories, sought a high tariff. Their key argument was that startup factories, or "infant industries", would at first be less efficient than European (British) producers. Furthermore, American factory workers were paid higher wages than their European competitors. The arguments proved highly persuasive in industrial districts. Clay's position was adopted in the 1828 and 1832 Tariff Acts. The Nullification Crisis forced a partial abandonment of the Whig position. When the Whigs won victories in the 1840 and 1842 elections, taking control of Congress, they re-instituted higher tariffs with the Tariff of 1842. In examining these debates Moore finds that they were not precursors to Civil War. Instead they looked backward and continued the old debate whether foreign trade policy should embrace free trade or protectionism.