Keystone is a city in Benton County, Iowa, United States. The population was 599 at the time of the 2020 census. It is part of the Cedar Rapids Metropolitan Statistical Area. History Keystone was platted in 1881 when the Chicago, Milwaukee, and St. Paul Railroad was extended to that point. Geography Keystone is located at . According to the United States Census Bureau, the city has a total area of , all land. Demographics 2010 census As of the census of 2010, there were 622 people, 250 households, and 165 families living in the city. The population density was . There were 280 housing units at an average density of . The racial makeup of the city was 99.2% White, 0.5% Native American, 0.2% Asian, and 0.2% from two or more races. Hispanic or Latino of any race were 0.6% of the population. There were 250 households, of which 30.8% had children under the age of 18 living with them, 53.2% were married couples living together, 8.8% had a female householder with no husband present, 4.0% had a male householder with no wife present, and 34.0% were non-families. 32.0% of all households were made up of individuals, and 20.4% had someone living alone who was 65 years of age or older. The average household size was 2.34 and the average family size was 2.93. The median age in the city was 42.8 years. 24% of residents were under the age of 18; 5.9% were between the ages of 18 and 24; 23% were from 25 to 44; 22.7% were from 45 to 64; and 24.4% were 65 years of age or older. The gender makeup of the city was 45.0% male and 55.0% female. 2000 census As of the census of 2000, there were 687 people, 273 households, and 174 families living in the city. The population density was . There were 281 housing units at an average density of . The racial makeup of the city was 99.42% White, 0.15% African American, and 0.44% from two or more races. Hispanic or Latino of any race were 0.29% of the population. There were 273 households, out of which 30.4% had children under the age of 18 living with them, 55.3% were married couples living together, 6.2% had a female householder with no husband present, and 35.9% were non-families. 32.6% of all households were made up of individuals, and 22.7% had