As of the census of 2000, there were 39,018 people, 13,081 households, and 6,566 families residing in the city. The population density was 3,093.9 people per square mile (1,194.7/km²). There were 13,619 housing units at an average density of 1,079.9/sq mi (417.0/km²). The racial makeup of the city was 73.00% White, 9.08% African American, 0.24% Native American, 4.62% Asian, 0.13% Pacific Islander, 4.35% from other races, and 2.09% from two or more races. Hispanic or Latino of any race were 9.04% of the population.
There were 13,081 households out of which 25.9% had children under the age of 18 living with them, 37.0% were married couples living together, 9.4% had a female householder with no husband present, and 49.8% were non-families. 29.6% of all households were made up of individuals and 7.3% had someone living alone who was 65 years of age or older. The average household size was 2.42 and the average family size was 3.02.
In the city the population was spread out with 16.9% under the age of 18, 39.2% from 18 to 24, 23.8% from 25 to 44, 12.0% from 45 to 64, and 8.1% who were 65 years of age or older. The median age was 23 years. For every 100 females there were 97.9 males. For every 100 females age 18 and over, there were 96.1 males.
The median income for a household in the city was $35,153, and the median income for a family was $53,017. Males had a median income of $36,255 versus $26,422 for females. The per capita income for the city was $16,261. About 9.0% of families and 21.3% of the population were below the poverty line, including 11.2% of those under age 18 and 5.4% of those age 65 or over.
DeKalb forms the western anchor of the I-88 corridor. It holds an important spot on the tollway as the location of both a toll plaza and an oasis which includes restaurants and a gas station. It is 30 miles away from Aurora and 65 miles from downtown Chicago and O'Hare International Airport. Voluntary Action Center provides two types of transportation services, TRANS-VAC and MED-VAC. TRANS-VAC provides transportation to activities and businesses in DeKalb County and has one bus route (the green line) that runs a regular hourly route Monday through Friday and some limited evening hours for special needs persons. MED-VAC provides transportation to out-of-town medical appointments when the client registers in advance for the ride. NIU Huskie Bus Line Serves NIU and the DeKalb area. It has the second highest rider-per-mile bus system in Illinois (behind the CTA). It is said to be the largest student-run bus system in the US (although it is operated by Veolia Transportation, it is operated locally).
DeKalb Taylor Municipal Airport (DTMA) or (KDKB), serving the general aviation community, is located at 3232 Pleasant Street, DeKalb, Illinois.