Keystone is a city in Benton County, Iowa, United States. The population was 687 at the 2000 census. It is part of the Cedar Rapids Metropolitan Statistical Area.
Keystone is located at 42°00′03″N 92°11′55″W / 42.000915°N 92.198544°W / 42.000915; -92.198544.
According to the United States Census Bureau, the city has a total area of 0.4 square miles (1.0 km²), all of it land.