Iowa State Route 21 is a north-south highway in South-Central Black Hawk County. This runs from Waterloo to the Black Hawk/Tama County Line. IA St Rt 21 passes through the following town in Black Hawk County. Waterloo
IA St Rt 21 intersects the following highways in Black Hawk County. U.S. Rt. 20, at Waterloo. Iowa State Route 27, at Waterloo.
