Michigan State Route 21 runs east-west in Central Ionia County. It runs from the Kent/Ionia County Line, near Lowell, to the Clinton/Ionia County Line, near Pewamo. MI St Rt 21 passes through the following towns in Ionia County. Ionia
Muir Pewamo MI St Rt 21 is multi-plexed in Ionia County. Michigan State Route 66, at Ionia. MI St Rt 21 intersects the following highways in Ionia County. Michigan State Route 66, at Ionia.
EB MI St Rt 21 at the Kent/Ionia County Line. WB MI St Rt 21 west of Saranac. A junction marker on SB MI St Rt 66. EB MI St Rt 21/SB MI St Rt 66 at south MI St Rt 66.
