The Tariff Act of 1930 signed into law by U.S. President Herbert Hoover on 17 June 1930 were duties (taxes) placed on over 20,000 imported goods. It’s political intent was to preserve American jobs, particularly in the agricultural sector, by discouraging foreign imports. Quoting the US Dept of State on the origin of the Act:
During the 1928 election campaign, Republican presidential candidate Herbert Hoover pledged to help the beleaguered farmer by, among other things, raising tariff levels on agricultural products. But once the tariff schedule revision process got started, it proved impossible to stop. Calls for increased protection flooded in from industrial sector special interest groups, and soon a bill meant to provide relief for farmers became a means to raise tariffs in all sectors of the economy. When the dust had settled, Congress had agreed to tariff levels that exceeded the already high rates established by the 1922 Fordney-McCumber Act and represented among the most protectionist tariffs in U.S. history. Smoot-Hawley did nothing to foster trust and cooperation among nations in either the political or economic realm during a perilous era in international relations.