Indiana State Route 18 runs east-west across Carroll County. It runs from the Carroll/White County Line, near Springboro, to the Carroll/Cass County Line, near Young America. This runs mostly across the middle part of the county. IN St Rt 18 passes through the following towns in Carroll County. Springboro Delphi
Flora Wheeling IN St Rt 18 is mutli-plexed in Carroll County. U.S. Rt. 421, from near Springbroro to near Delphi. Indiana State Route 39, from near Springboro to near Delphi.