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. A BGS on EB I-72/NB U.S. Rt. 51. A BGS on EB I-72/NB U.S. Rt. 51. A BGS on EB I-72/NB U.S. Rt. 51. A BGS on WB I-72/SB U.S. Rt. 51. A set of guide markers on the ramp from WB I-72/U.S. Rt. 51 to IL St Rt 121. SB IL St Rt 121 near Decatur. NB IL St Rt 48/SB IL St Rt 121 at Main Street. A junction marker on SB BUSN U.S. Rt. 51. SB IL St Rt 48/NB IL St Rt 121 at the CN railroad underpass in 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. EB IL St Rt 105/NB IL St Rt 121 at N Street. A BGS on WB IL St Rt 105/SB IL St Rt 121. A junction marker on EB IL St Rt 105. A junction marker on EB U.S. Rt. 36. A BGS on EB U.S. Rt. 36/SB IL St Rt 121, in Decatur. A BGS on WB U.S. Rt. 36. NB IL St Rt 121 south of east U.S. Rt. 36. SB IL St Rt 121 south of east U.S. Rt. 36. 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.
