The history of St. Louis, Missouri, from 1905 to 1980 saw declines in population and economic basis, particularly after World War II. Although St. Louis made civic improvements in the 1920s and enacted pollution controls in the 1930s, suburban growth accelerated and the city population fell dramatically from the 1950s to the 1980s. Like many urban areas, St. Louis experienced high unemployment during the Great Depression, then expanded its industrial base during World War II. The city became home to Gateway Arch National Park (then known as the Jefferson National Expansion Memorial) during the 1930s, and during the 1960s the Gateway Arch was built on the memorial grounds. St. Louis City and St. Louis County made multiple attempts at consolidation during the period, but none were particular