Frankfort is an affluent village in Will and Cook Counties, Illinois, United States. The population was 10,391 at the 2000 census. The population according to Forbes. com was 16,928 in 2006. Also, according to Forbes. com, the village ranks as the 36th fastest growing suburb in the United States. In addition to the current population growth, the Northeastern Illinois Planning Commission has forecast the population to reach 55,797 in 2030.