Illinois State Route 121 runs in a angle across Macon County. This highway enters Macon County from Logan County in the northwest portion. Then it exits into Moultrie County in the southeast region. IL St Rt 121 passes through the following towns in Macon County. Warrensburg
EB IL St Rt 121 at the Logan/Macon County Line. EB IL St Rt 121 west of Warrenburg. A BGS on EB I-72/NB U.S. Rt. 51. SB IL St Rt 121 near Decatur. A junction marker on SB IL St Rt 48. SB IL St Rt 121 on the eastside of Decatur. SB IL St Rt 121 near Garfield in Decatur. A junction marker on EB IL St Rt 105. A BGS on EB U.S. Rt. 36/SB IL St Rt 121, in Decatur. WB IL St Rt 121 in Mt. Zion. WB IL St Rt 121 near Hervey City. WB IL St Rt 121 at the Macon/Moultrie Line.