Keystone is a city in Benton County, Iowa, United States.

Keystone was platted in 1881 when the Chicago, Milwaukee, and St. Paul Railroad was extended to that point.

[4] According to the United States Census Bureau, the city has a total area of 0.45 square miles (1.17 km2), all land.

There were 278 housing units at an average density of 620.3 per square mile (239.5/km2).

There were 280 housing units at an average density of 622.2 per square mile (240.2/km2).

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.

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 racial makeup of the city was 99.42% White, 0.15% African American, and 0.44% from two or more races.

32.6% of all households were made up of individuals, and 22.7% had someone living alone who was 65 years of age or older.