Aurora is a city in the Chicago metropolitan area located partially in DuPage, Kane, Kendall, and Will counties in the U.S. state of Illinois. Located primarily in DuPage and Kane counties, it is the second most populous city in Illinois, after Chicago, and the 144th most populous city in the United States. The population was 197,899 at the 2010 census, and was 180,542 as of the 2020 Census. Founded within Kane County, Aurora's city limits have expanded into DuPage, Will, and Kendall counties.