Twenty years ago Philadelphia was a city in trouble-still corrupt, but no longer as contented as Lincoln Steffens had found it. The story of this last twenty years, from the earliest stirrings of reform to the renaissance of today, is a lesson to all cities. Those who have developed its planning process have thereby also contributed significantly to planning theory and practice. Philadelphia's development is a story of people and of two political leaders. Without these leaders, it might not have taken place, and it may decline when they move on, as one of them already has. The movement has its chance for survival and continuity in the rise of the new “professional citizen,” a “fourth power” outside the governmental structure, not unique to Philadelphia but particularly flourishing there.