SBI Route 181 was Palestine to US-50 near Vincennes IN. This was changed to IL-33 in 1948.
SBI Route 182 was Centralia to IL-37. In 1941 IL-161 was extended east from Centralia replacing IL-182.
SBI Route 183 was Sesser to Whittington. In 1984 this was changed to IL-154 as an extension of that route. In 1970 several creeks were dammed and Rend Lake was formed. IL-183 was rebuilt to bridge this new lake.
SBI Route 184 was (and IL-184 still is) Mulkeytown to Royalton in Franklin County.
SBI Route 185 was Bluff City to Farina. In 1949 it was extended NW to Hillsboro. The part from Bluff City to and thru Vandalia was on US-40, and the rest on an unnumbered route.

IL-185 was the last SBI Route in IL.

All further numbers were assigned after the SBI program ended.

IL-186 was used from 1938 to 1945 on a road later numbered IL-170 from Seneca to Budd in LaSalle and Livingston Counties.
IL-190 was used on the East-West Tollway from the Tri-State Tollway to Sugar Grove from 1966 to 1971. This route had been Toll-US-30 before IL-190. In 1972 IL-190 was changed to IL-5, and then in 1990 it was changed again to I-88.
I-190 was used on the spur into O'Hare Airport after 1980. Previously this spur had been IL-594 (1971 to 1980). From 1960 to 1970 IL-194 was used on the Airport Spur, until IL-194 was extended west on the NW Tollway.
IL-192 was used in 1955 to designate the old alignment of IL-92 from US-67 to west of Edington in Rock Island County. This is still the same route.
IL-194 was used on the Kennedy Expressway in Chicago from the Edens Junction into O'Hare Airport 1960 to 1970. In 1971 IL-194 from the Tri-State into the airport was changed to IL-594 (Later I-190), and IL-194 was extended west on the Northwest Tollway to IL-53 near Schaumburg. In the mid 1970's I-90 was rerouted to it's current route on the Kennedy and Northwest Tollway, and IL-194 was no more...
IL-199 was used from 1969 to 1980 on a road from US-67 to IL-92 in Milan and Rock Island. This was changed to IL-92 when IL-92 was rerouted in 1980. This was the freeway along the river.

Route overview and markers

Updated 11-18-2007