Rock Falls is a city in Whiteside County, Illinois, United States. The recorded population was 8,606 at the 2020 census, down 7.12% from 9,266 in 2010. The city is located on the Rock River, directly opposite its twin city of Sterling. Geography Rock Falls is separated from its twin city, Sterling, to the North by the Rock River. According to the 2010 census, Rock Falls has a total area of , of which (or 96.44%) is land and (or 3.56%) is water. Demographics At the 2000 census there were 9,580 people, 3,895 households, and 2,559 families living in the city. The population density was . There were 4,098 housing units at an average density of . The racial makeup of the city was 91.78% White, 0.88% African American, 0.45% Native American, 0.26% Asian, 4.71% from other races, and 1.92% from two or more races. Hispanic or Latino of any race were 11.54%. Of the 3,895 households 30.7% had children under the age of 18 living with them, 47.5% were married couples living together, 13.7% had a female householder with no husband present, and 34.3% were non-families. 29.4% of households were one person and 13.9% were one person aged 65 or older. The average household size was 2.43 and the average family size was 2.99. The age distribution was 25.5% under the age of 18, 9.0% from 18 to 24, 27.6% from 25 to 44, 21.9% from 45 to 64, and 15.9% 65 or older. The median age was 36 years. For every 100 females, there were 90.8 males. For every 100 females age 18 and over, there were 87.5 males. The median household income was $34,442 and the median family income was $41,803. Males had a median income of $32,733 versus $21,092 for females. The per capita income for the city was $16,524. About 10.3% of families and 11.5% of the population were below the poverty line, including 14.8% of those under age 18 and 6.8% of those age 65 or over. Education Rock Falls has 4 school districts. Rock Falls Elementary School District #13 consists of Riverdale Preschool Center, Dillon Elementary School, Merrill Intermediate School, and Rock Falls Middle School. East Coloma-Nelson CESD #20 operates East Coloma-Nelson grade school. Montmorency CCSD #145 operates Montmorency grade school. Thome School serves as the towns special needs institution. The Roman Catholic Diocese of Rockford runs one school in the city: St. Andrew's