According to the 2010 census, the city has a total area of 7.15 square miles (18.5 km2), of which 6.98 square miles (18.1 km2) (or 97.62%) is land and 0.17 square miles (0.44 km2) (or 2.38%) is water.
Wood River is located on the Mississippi River approximately 15 miles (24 km) upstream of downtown St. Louis, Missouri, among several contiguous cities and villages that have come to be known as the "Riverbend" area. The current confluence of the Mississippi and the Missouri rivers is just south of one of these neighboring villages, Hartford. Other cities making up the "Riverbend" include Alton, East Alton, Godfrey, Roxana and Bethalto.
As of the census of 2000, there were 11,296 people, 4,725 households, and 2,995 families residing in the city. The population density was 1,865.2 people per square mile (719.7/km²). There were 5,001 housing units at an average density of 825.8 per square mile (318.6/km²). The racial makeup of the city was 97.57% White, 0.63% African American, 0.27% Native American, 0.45% Asian, 0.35% from other races, and 0.73% from two or more races. Hispanic or Latino of any race were 1.21% of the population.
There were 4,725 households out of which 29.9% had children under the age of 18 living with them, 46.2% were married couples living together, 13.0% had a female householder with no husband present, and 36.6% were non-families. 31.7% of all households were made up of individuals and 14.7% had someone living alone who was 65 years of age or older. The average household size was 2.36 and the average family size was 2.96.
In the city the population was spread out with 24.1% under the age of 18, 10.2% from 18 to 24, 28.7% from 25 to 44, 20.1% from 45 to 64, and 16.9% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 90.3 males. For every 100 females age 18 and over, there were 86.6 males.
The median income for a household in the city was $33,875, and the median income for a family was $41,688. Males had a median income of $35,097 versus $24,522 for females. The per capita income for the city was $18,098. About 13.2% of families and 14.8% of the population were below the poverty line, including 21.2% of those under age 18 and 10.6% of those age 65 or over.