From Philadelphia to Seattle, American cities are banking on parks and public spaces to drive social and economic progress. “Parks may not seem particularly urgent compared with the latest gangland murder epidemic; but the effort in Chicago to improve and expand them has, neighborhood by neighborhood, delivered long-term rewards. A few downtown showpieces, like the urbane Riverwalk and glamorous Millennium Park, have reaped immense financial windfalls for the city. Barack Obama’s presidential library in Jackson Park promises to become a major new attraction and help rejuvenate that part of the South Side.”