As of the census of 2000, there were 7,996 people, 2,610 households, and 1,853 families residing in the city. The population density was 1,498.2 people per square mile (578.1/km²). There were 2,723 housing units at an average density of 510.2/sq mi (196.9/km²). The racial makeup of the city was 76.25% White, 0.85% African American, 0.38% Native American, 1.43% Asian, 0.01% Pacific Islander, 18.76% from other races, and 2.33% from two or more races. Hispanic or Latino of any race were 37.81% of the population.
There were 2,610 households out of which 39.7% had children under the age of 18 living with them, 53.8% were married couples living together, 11.1% had a female householder with no husband present, and 29.0% were non-families. 24.0% of all households were made up of individuals and 10.1% had someone living alone who was 65 years of age or older. The average household size was 3.05 and the average family size was 3.56.
In the city the population was spread out with 30.1% under the age of 18, 12.7% from 18 to 24, 31.3% from 25 to 44, 16.8% from 45 to 64, and 9.1% who were 65 years of age or older. The median age was 29 years. For every 100 females there were 107.5 males. For every 100 females age 18 and over, there were 105.9 males.
The median income for a household in the city was $44,363, and the median income for a family was $48,087. Males had a median income of $30,578 versus $23,750 for females. The per capita income for the city was $17,253. About 6.9% of families and 9.1% of the population were below the poverty line, including 11.2% of those under age 18 and 1.2% of those age 65 or over.
U.S. Route 14, locally known as the Northwest Highway, runs north-south through Harvard. Illinois Route 23 begins in southern Harvard and connects the city with other locations to the south. Illinois Route 173 also runs east-west through Harvard, and it connects many other towns along the Wisconsin border to Harvard. The nearest Interstate Highway to Harvard is Interstate 90 in Belvidere; Interstate 39 is also nearby, as is Interstate 43 in Wisconsin.
Harvard is also served by multiple forms of public transportation. Pace operates Route 808 in Harvard. This route links the city to the communities of Woodstock and Crystal Lake. Metra's Union Pacific/Northwest Line has a station in Harvard and operates daily service to Chicago's Ogilvie Transportation Center. The Harvard station is the most remote point in the Metra system at 62.8 miles (101 km) from downtown Chicago.