Burnham and Bennett observed that "there exist between this city and outlying towns within a certain radius vital and almost organic relations." What set their Plan of Chicago apart from earlier ideas was its bold embrace of the entire region, not just the city center. In the fall of 1909, the Chicago Plan Commission took charge of implementing the plan within the city limits. For the broader region, citizens established the Chicago Regional Plan Association in 1923, headed by Daniel Burnham's son. The plan soon reached beyond the region, as metropolitan areas across the United States created regional planning associations inspired by its principles.