St. Louis city planners, faced with problems of aging buildings and decaying neighborhoods, implemented a variety of redevelopment projects throughout the 20th century. During the 1920s and 1930s, city leaders often focused on beautification of the city and creating grand public spaces by tearing down dilapidated buildings. This strategy resulted in the Civic Center around Memorial Plaza, as well as redevelopment of the riverfront and the Jefferson National Expansion Memorial site. In the post-war period, city planners continued to redevelop large areas in hopes of revitalizing the city. Large-scale slum clearance efforts took areas or neighborhoods declared obsolete, such as Mill Creek Valley, and demolished them in their entirety in order to rebuild with new industry, commerce, and housing projects. Construction of new infrastructure and public buildings also necessitated the clearance of large areas of older buildings. Neighborhoods that were not yet deemed obsolete, such as Hyde Park, were designated as redevelopment areas, and various clean up and rehabilitation programs were undertaken in these areas.