Viola is a village in Mercer County, Illinois, United States. The population was 955 at the 2010 census, a decline of one person from 956 in 2000.Viola is located at 41°12′14″N 90°35′5″W / 41.20389°N 90.58472°W / 41.20389; -90.58472.According to the 2010 census, Viola has a total area of 0.855 square miles, of which 0.84 square miles is land and 0.015 square miles is water.As of the census of 2000, there were 956 people, 383 households, and 274 families residing in the village. The population density was 1,155.8 people per square mile. There were 401 housing units at an average density of 484.8 per square mile. The racial makeup of the village was 98.22% White, 0.84% from other races, and 0.94% from two or more races. Hispanic or Latino of any race were 1.78% of the population.There were 383 households out of which 32.6% had children under the age of 18 living with them, 60.1% were married couples living together, 8.9% had a female householder with no husband present, and 28.