Significant policies that influenced the economic landscape post-World War I include the introduction of protectionist tariffs, like the Fordney-McCumber Tariff, which aimed to boost domestic production but led to retaliatory tariffs and strained international trade. Additionally, the Federal Reserve's monetary policies, including addressing inflation and interest rates, played a crucial role. These factors, alongside war reparations imposed on Germany and the global economic instability, contributed to the rise of the Great Depression in the 1930s, reshaping economic systems worldwide.