Illinois State Route 123 was extened back into Sangamon County in October, 2003. This runs along a old alignment of Illinois State Route 124. Then a previously un-numbered highway from the junction with IL St Rt 124 to I-55 at Williamsville. Tourist traffic now can take IL St Rt 123 from I-55 to Lincoln's New Salem Historical Site. IL St Rt 123 passes through the following towns in Sangamon County. Williamsville IL St Rt 123 is multi-plexed in Sangamon County. Illinois State Route 29, near Athens.