is a city in Will County and Kendall County in the U.S. state of Illinois, located southwest of Chicago. It is the county seat of Will County. As of the 2000 census, the city had a total population of 106,221. Its estimated population in 2007 was 145,800. It continues to be Illinois' fastest growing city and one of the fastest growing in the United States. Back when Joliet was first platted in the early 1830's, it was still in Cook County until 1836, when it became the county seat of the new Will County.
In 1833, following the Black Hawk War, Charles Reed built a cabin along the west side of the Des Plaines River. Across the river in 1834, James B. Campbell, treasurer of the canal commissioners, laid out the village of "Juliet", a name local settlers had been using before his arrival. Just before the depression of 1837, Juliet incorporated as a village, but to cut tax expenses, Juliet residents soon petitioned the state to rescind that incorporation. In 1845, local residents changed the community's name from "Juliet" to "Joliet". Joliet was reincorporated as a city in 1852. Possible sources of the name include the Shakespearean character "Juliet", as the nearby village of Romeoville was named as a companion; however, it was most likely a corruption of the name of French Canadian explorer Louis Jolliet, who in 1673, along with Father Jacques Marquette, paddled up the Des Plaines River and camped on a huge mound, a few miles south of present-day Joliet. Maps from Jolliet's exploration of the area, placed a large hill or mound on what is now the southwest corner of the city. That hill was named Mound Jolliet and was made up entirely of clay. The spot was mined by early settlers and is now a depression. That depression was settled soon after and became known as the town of Rockdale.