Highland Park is a city in the Moraine Township of Lake County, Illinois, United States. The population was 31,365 at the 2000 census. It now has 33,492 citizens as of September 28, 2009. Highland Park is one of several affluent towns on the North Shore of Chicago. The city evolved from two settlements: St. John and Port Clinton, but the main downtown area was known as Port Clinton and was a lumber port.