According to the United States Census Bureau, the city has a total area of 6.9 square miles (17.9 km²), of which, 6.9 square miles (17.8 km²) of it is land and 0.1 square miles (0.2 km²) of it (1.01%) is water.
In the early 19th century, DuQuoin was near the Lusk's Ferry Road, an important, early road that connected Kaskaskia with Lusk's Ferry on the Ohio River. The road ran easterly out of Steeleville to a point southwest of DuQuoin. There it turned to the southeast to cross the Big Muddy River and head for Lusk's Ferry.
The DuQuoin High Schools mascot is the Indians, from the people that settled the land before the city. The Indians have outstanding football and track programs. As of October 2007 the Indians hold the Illinois State Record for most consecutive playoff appearances, going to the playoffs 24 years in a row and won state championships in football in 1988 and 1992
In 2006, the DuQuoin Middle School Warriors won the Southern Illinois Junior High School Athletic Association (SIJHSAA) State Basketball Tournament, beating Olney in the final round. The Warriors never lost a game that season, going 26-0.
The area east of Du Quoin is known as "Old Du Quoin" The actual City of Du Quoin was founded in 1853 as the people of what is now Old Du Quoin moved the town west to avail themselves of the Illinois Central Railroad lines that were being laid. The city government is a commission form of government with a mayor and four commissioners. Du Quoin is the largest community in Perry County.
DuQuoin High School football standout Nick Hill signed a contract with the Chicago Bears of the National Football League.
There were 2,716 households out of which 28.0% had children under the age of 18 living with them, 45.0% were married couples living together, 12.4% had a female householder with no husband present, and 39.3% were non-families. 35.6% of all households were made up of individuals and 19.9% had someone living alone who was 65 years of age or older. The average household size was 2.26 and the average family size was 2.92.
In the city the population was spread out with 23.5% under the age of 18, 10.2% from 18 to 24, 24.9% from 25 to 44, 20.7% from 45 to 64, and 20.8% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 89.4 males. For every 100 females age 18 and over, there were 84.8 males.
The median income for a household in the city was $29,124, and the median income for a family was $37,688. Males had a median income of $33,576 versus $18,958 for females. The per capita income for the city was $14,883. About 13.3% of families and 18.1% of the population were below the poverty line, including 22.6% of those under age 18 and 12.1% of those age 65 or over.