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
During the 1870s and 1880s, the United States was Europe's largest supplier of cereals. There was an increasing trade imbalance between Europe and the United States until the 1900s, given that the United States had remained protectionist. The United States was (almost) free trade before 1861, and high tariff afterwards. It experienced a period of strong growth while Europe was in the midst of a depression. Around 1870, Europe's trade deficit with America represented 5% to 6% of the region's imports. It reached 32% in 1890 and 59% around 1900.