In this Aug. 18, 2009, aerial photo is downtown Pittsburgh located at the confluence of the Allegheny, Monongahela and Ohio rivers on the north side of Pittsburgh. (AP Photo/Gene J. Puskar) Blue-collar workers poured into the cavernous auto plants of Detroit for generations, confident that a sturdy back and strong work ethic would bring them a house, a car and economic security. It was a place where the American dream came true. It came true in cities across the industrial heartland, from Chicago’s meatpacking plants to the fire-belching steel mills of Cleveland and Pittsburgh. It came true for decades, as manufacturing brought prosperity to big cities in states around the Great Lakes and those who called them home. Detroit was the affluent capital, a city with its own emblematic musical sound and a storied union movement that drew Democratic presidential candidates to Cadillac Square every four years to kick off their campaigns at Labor Day rallies.