The article discusses how US trade policy has changed over time, mainly using import tariffs for different reasons like raising money for the government, protecting local businesses, and making deals with other countries to lower trade barriers. These goals have shifted in importance over history, influenced by where trade interests are strongest and how much power those areas have in Congress. The article also looks at how tariffs can hurt the economy, how protectionism helped US industries grow, and how high tariffs may have worsened the Great Depression in the 1930s.