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
The Republican high tariff advocates appealed to farmers with the theme that high-wage factory workers would pay premium prices for foodstuffs. This was the "home market" idea, and it won over most farmers in the Northeast, but it had little relevance to the southern and western farmers who exported most of their cotton, tobacco and wheat. In the late 1860s the wool manufacturers (based near Boston and Philadelphia) formed the first national lobby, and cut deals with wool-growing farmers in several states. Their challenge was that fastidious wool producers in Britain and Australia marketed a higher quality fleece than the Americans, and that British manufacturers had costs as low as the American mills. The result was a wool tariff that helped the farmers by a high tariff rate on imported wool—a tariff the American manufacturers had to pay—together with a high tariff on finished woolens and worsted goods.