Monmouth is a city in and the county seat of Warren County, Illinois, United States. The population was 9,444 at the 2010 census, down from 9,841 in 2000. It is the home of Monmouth College and contains Monmouth Park, Harmon Park, North Park, Warfield Park, West Park, South Park, Garwood Park, Buster White Park and the Citizens Lake & Campground. It is the host of the Prime Beef festival, held annually the week after Labor Day. The festival is kicked off with one of the largest parades in Western Illinois. Monmouth is also known regionally as the “Maple City”. It is part of the Galesburg Micropolitan Statistical Area.
Monmouth is located at 40°54′42″N 90°38′40″W / 40.91167°N 90.64444°W / 40.91167; -90.64444 (40.911531, -90.644579). Monmouth is located in Western Illinois where US Route 34, US Route 67, Illinois Route 164, and now the new Chicago to Kansas City Expressway (Illinois Route 110) intersect.
According to the 2010 census, Monmouth has a total area of 4.231 square miles (10.96 km), of which 4.21 square miles (10.90 km) (or 99.5%) is land and 0.021 square miles (0.05 km) (or 0.5%) is water.
As of the census of 2000, there were 9,841 people, 3,688 households, and 2,323 families residing in the city. The population density was 2,442.3 people per square mile (942.8/km²). There were 3,986 housing units at an average density of 989.2 per square mile (381.9/km²). The racial makeup of the city was 92.72% White, 2.80% African American, 0.23% Native American, 0.47% Asian, 0.19% Pacific Islander, 1.91% from other races, and 1.67% from two or more races. Hispanic or Latino of any race were 4.35% of the population.
There were 3,688 households out of which 29.6% had children under the age of 18 living with them, 47.7% were married couples living together, 11.5% had a female householder with no husband present, and 37.0% were non-families. 32.1% of all households were made up of individuals and 14.9% had someone living alone who was 65 years of age or older. The average household size was 2.37 and the average family size was 2.99.
In the city the population was spread out with 23.0% under the age of 18, 17.1% from 18 to 24, 24.1% from 25 to 44, 20.3% from 45 to 64, and 15.5% who were 65 years of age or older. The median age was 34 years. For every 100 females, there were 88.5 males. For every 100 females age 18 and over, there were 85.3 males.
The median income for a household in the city was $33,641, and the median income for a family was $41,004. Males had a median income of $30,006 versus $20,144 for females. The per capita income for the city was $15,839. About 8.0% of families and 11.1% of the population were below the poverty line, including 14.5% of those under age 18 and 6.1% of those age 65 or over.