Marengo is a city in McHenry County, Illinois, United States approximately 60 miles west northwest of Chicago. The population was 7,648 as of the 2010 census.
Marengo is located at 42°15′3″N 88°36′18″W / 42.25083°N 88.60500°W / 42.25083; -88.60500.
According to the 2010 census, Marengo has a total area of 5.01 square miles (12.98 km), all land.
As of the census of 2000, there were 6,355 people, 2,387 households, and 1,694 families residing in the city. The population density was 1,598.5 people per square mile (616.5/km²). There were 2,475 housing units at an average density of 622.6 per square mile (240.1/km²). The racial makeup of the city was 92.07% White, 0.30% African American, 0.27% Native American, 0.28% Asian, 0.02% Pacific Islander, 5.54% of other races, and 1.53% of two or more races. Hispanic or Latino of any race were 13.00% of the population.
There were 2,387 households out of which 38.6% had children under the age of 18 living with them, 55.9% were married couples living together, 10.7% had a female householder with no husband present, and 29.0% were non-families. 24.9% of all households were made up of individuals and 9.8% had someone living alone who was 65 years of age or older. The average household size was 2.64 and the average family size was 3.17.
The population was spread out with 29.3% under the age of 18, 8.6% from 18 to 24, 31.0% from 25 to 44, 19.2% from 45 to 64, and 12.0% who were 65 years of age or older. The median age was 34 years. For every 100 females, there were 96.3 males. For every 100 females age 18 and over, there were 94.3 males.
The median income for a household in the city was $50,214, and the median income for a family was $57,209. Males had a median income of $41,298 versus $26,317 for females. The per capita income for the city was $22,225. About 3.9% of families and 4.4% of the population were below the poverty line, including 5.4% of those under age 18 and 5.5% of those age 65 or over.