crosses the Big Muddy River as a four-lane divided highway. Near downtown Carbondale, the road then becomes a six-lane divided highway, then undivided, and then a seven-lane undivided highway. The route then splits into a one-way pair (westbound traffic serves Main Street; eastbound traffic serves Walnut Street). It then intersects US 51 as another one-way pair. Carbondale to Kentucky state line After passing through Carbondale, IL 13 then proceeds to pass through Carterville, Crainville, and Herrin. It then intersects IL 148 southwest of the Veterans Airport of Southern Illinois. In Marion, it then meets I-57 at a SPUI and then IL 37 at a signalized intersection. Beyond that, IL 13 intersects IL 166 in between Marion and Crab Orchard. It then proceeds eastward towards Harrisburg. In Harrisburg, IL 34 runs concurrently with IL 13 before intersecting with US 45. At that point, IL 34 turns south along US 45. Near Equality, IL 13 intersects IL 142. In between Equality and Junction, it then intersects IL 1. Then, the route continues eastward through Shawneetown and then Old Shawneetown before crossing the Shawneetown Bridge over the Ohio River. At that point, IL 13 becomes KY 56. History The state of Illinois was founded in 1818. One of its first governmental tasks was the construction of primitive dirt roads between the three pioneer villages of Cahokia, Kaskaskia, and Shawneetown. Illinois Route 13 is a distant descendant of most of the Cahokia-Shawneetown route and has a claim to be one of the oldest state highways in Illinois. Illinois Route 13 did not take its current physical form, though, until after the enactment of the Good Roads Movement paving program in 1918. The statewide plan standardized the alignment of this road and numbered it Illinois 13. Except for a few alignment changes, Illinois 13 has remained the same since its inception in 1918. In 1937 it was rerouted around Sparta (now Illinois Route 4 and Illinois Route 154), replacing a large chunk of Illinois Route 152 in the process. Another reroute took place between 1944 and 1947 when Illinois 13 took over a new highway (then called U.S. Route 460) in and around Belleville. The old route became Alternate Illinois 13. In 1947 it was moved back to Bond Avenue. Later, U.S. 460 would be dropped and replaced with Illinois Route 15. Harrisburg Bypass To address congestion in downtown Harrisburg, the Illinois Department of Transportation