Illinois State Route 129 was commisioned to replace sections of U.S. Rt. 66, when that was decommisoned. IL St Rt 129 at one time ran from Gardner in Grundy County, to near Wilmington in Will County. Near Gardner, IL St Rt 129 went over a big green bridge over the Pequot Spur of the Union Pacific Railroad (ex Chicago & Alton; Gulf Mobile, & Ohio; Illinois Central & Gulf; Southern Pacific) and the Mazon River. This bridge was part of the U.S. Rt. 66 days and was deemed to costly to repair. The bridge was removed and IL St Rt 129 was pulled back to end at IL St Rt 113 in Braidwood.
On September 30th, 2011 the ramp from SB I-55 to SB IL St Rt 129 was closed, with no plan to re-open until the I-55/IL St Rt 129 interchange is re-built. Traffic is guided south along I-55 to Exit 236/IL St Rt 113, then east along Coal City Road to rejoin IL St Rt 129.
A old & new street sign at Gardner that still labels a portion of road as IL St Rt 129.
A mile marker on the old portion of IL St Rt 129 between Braidwood and Braceville.
IL St Rt 129 passes through the following towns in Will County. Braidwood
IL St Rt 129 does not multi-plex with any other highway in Will County. IL St Rt 129 intersects the following highways in Will County. Interstate 55, near Wilmington.