SBI Route 21 was Antioch to Chicago via the following current routes:

• IL-83, Antioch to Grayslake;
• IL-137, Grayslake to Libertyville;
• IL-21, Libertyville to Niles; Milwaukee Ave,
• IL-43 to Elston Av. in Chicago
• Elston Av., Milwaukee Av. to the Loop.
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• (IL-21 was only posted south of US-45 in what is now Prospect Hts., until 1940.)
• In 1940: IL-21 was added to US-45, Prospect Hts. to Half Day (Now Lincolnshire) (Milwaukee Av.) and continued north replacing US-45 north of Half Day when US-45 was changed to a new highway. North of Libertyville, IL-21 was applied to a new road to Grayslake, and then replaced IL-54 from Grayslake to Antioch. (The rest of IL-54 was changed to IL-83 in 1941.)
• In 1963: IL-21 was dropped Grayslake to Antioch in favor of the second number, IL-83.
• In 1972: IL-21 was removed from IL-43 in Niles into Chicago.
• In 1973: IL-21 replaced IL-63 from Libertyville to Gurnee, and IL-137 replaced IL-21 from Libertyville to Grayslake. This was part of the removal of all of IL-63 during the Great Purge.

IL-21 runs in Cook and Lake Counties.

SBI Route 22 was originally a loop around the area, called the "22 Loop" on the following current routes:

• US-41, Waukegan to Highland Park;
• IL-22, Highland Park to Fox River Grove;
• US-14, Fox River Grove to Crystal Lake;
• IL-31, Crystal Lake to Aurora and
• US-30, Aurora to Lynwood.
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• By 1935 IL-22 applied only to Fox River Grove-Highland Park-Waukegan.
• In 1937: US-41 was moved to it's current route, replacing IL-22 Highland Park to Waukegan.

IL-22 today goes Highland Park to Fox River Grove in Lake and McHenry Counties.

IL-22 is planned to be improved to 4 lanes for most of it's current length to alleviate huge traffic jams. NIMBY problems in Lincolnshire slowed things down, but in 2003 IL-22 is finally beng upgraded to 4 lanes on the east end. In 2006 the Lake Zurich bypass to the south of the town center was opened, while work continues east of there thru Hawthorn Woods, Long Grove and Buffalo Grove.

I-24 runs from a bridge over the Ohio River near Metropolis to I-57 near Goreville. The far eastern end of I-24 is at I-75 in Chattanooga TN. It runs for about 34 miles in IL.

While looking at I-24 just in IL, one may wonder why it was ever built, or why was it not extended directly to St. Louis, but if you look at it in the grander scheme of things you will see that it fits in pretty nicely for traffic heading SE towards Atlanta, Florida and the SE coast. By using I-64 and I-57, traffic from St. Louis has a pretty decent route to the SE. That explains why St. Louis is used as a control city on I-24 even though I-24 does not go there directly.

I-24 does violate one of the sacred rules of highway numbers, having the same number on a US highway as an interstate in the same state. US-24 runs thru IL as well, but a couple hundred miles north. While no confusion is made because of this transgression, this is the only place in the US that I know of where this occurs. (There is an extension of I-73 and/or I-74 that may cause a conflict in the SE US soon though)

SBI Route 25 was Kankakee to Fairfield, now part of US-45.

IL-25 runs from Carpentersville to Oswego in Kane and Kendall Counties, and has not changed since the late 1930's. This is on the east side of the Fox River (IL-31 runs on the west bank)

SBI Route 26 was Freeport to Polo, on part of current IL-26. 1937: IL-26 was extended Freeport to the WI line, in place of IL-74, and extended Polo to Bureau along US-52 to Dixon, and replacing IL-89 Dixon to Bureau. In 1969: Extended south to East Peoria replacing IL-87.

IL-26 was rerouted onto the nearby I-180 bridge over the Illinois River near Hennepin during the 1990’s. The older IL-26 bridge, half a mile south of I-180, was removed after 1999. the old approaches are now local roads, used mainly as access to riverside industries on both banks.

IL-26 runs from the WI Line north of Freeport to East Peoria thru Stephenson, Ogle, Lee, Bureau, Putnam, Marshall, Woodford and Tazewell counties.

SBI Route 29 was DePue to Peoria, on part of current IL-29.

• 1936: IL-29 was extended from Peoria to Pekin, replacing IL-24 here.
• In 1940: Extended Pekin to Pana, replacing the remainder of IL-24.
• In 1942: Extended Bureau Jct. to Spring Valley after US-6 moved to new highway.

IL-29 currently runs from Spring Valley to Pana in Bureau, Putnam, Marshall, Peoria, Tazewell, Mason, Menard, Sangamon, and Christian Counties.

SBI Route 30 was:

• US-150, Peoria to IL-91,
• IL-91, US-150 to Wyoming,
• IL-17, Wyoming to IL-78,
• IL-78, IL-17 to US-34,
• US-34, IL-78 to Galva.
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• In 1938 it was removed north of Toulon in favor of IL-17, and IL-30 was posted on former IL-93 to Kewaunee.
• 1941: Replaced in its entirety with IL-91.

Not used since 1941.

US-30 has gone thru many changes over the years. Originally it ran from Fulton IL east to Chicago and into IN on the following current day routes: US-30 Fulton to Sterling, IL-2 Sterling to Dixon, and IL-38 Dixon to Bellwood. From Bellwood to Indiana it ran on various city streets including Roosevelt Road and Stony Island Av. In the 1930's it was rerouted to a new road south of the original, pretty much on its current route to IN at Lansing. This process took several years, and went like this:

• In 1926: US-30 ran thru Chicago, North on Torrance from the IN line at IL-52 (Now IL-83) to the Loop and then west on Roosevelt to Geneva (west of Hillside it was on the current IL-38). It then ran west to Sterling on the current IL-38.
• In 1932: It was rerouted south of Chicago to Aurora via the Lincoln Highway, on its current route. North of Aurora it ran north on the current IL-31 to Geneva, then west to DeKalb and Sterling on the current IL-38 (The portion west of Geneva remained US-30). The old route became US-330.
• The next change was when the more direct route from Sterling to Aurora south of the original route was completed. The old road became US-330, as an extension to the then existing US-330.
• In 1942 US-330 became Alternate US-30.

In 1971 this Alternate US-30 became IL-38 west of US-12/US-45. East of here the number was removed. The portion of IL-31 from Aurora to Geneva was US-30 for a while, after US-30 was rerouted south of Chicago (thru Joliet) and before it was rerouted west of Aurora. IL-31 north of Geneva was US-430 at this time, and US-430 was changed to IL-31 before or at the same time as US-30 was rerouted west of Aurora. In the 1950's a new approach to and bridge over the Mississippi River was built and the old road became Alternate-US-30, then IL-136 (since the matching IA road was IA-136).

Also in the late 1950's US-30 was rerouted around Aurora, and the old road became City-US-30 then Business-US-30, and now is unnumbered. In 1971 the parts of Alternate-US-30 west of Bellwood (US-45) became IL-38, the rest lost the numbers altogether.

During the period 1963 to 1965, if one drove south on IL-31 from anywhere north of St. Charles to Oswego he would have crossed in succession: Alt-US-30 (now IL-38, and formerly US-330), Toll-US-30 (now I-88), Bus-US-30 (now Galena Blvd.), US-30 (still US-30). At the same time he would have been on what was once known as US-430 north of Geneva and US-30 south.

The Lincoln Highway runs from Coast to Coast, and in Illinois more or less followed the original US-30. US-30 was rerouted, and the current route of the original Lincoln Highway is as follows:

• US-30, Mississippi River at Fulton to Sterling.
• IL-2, Sterling to Dixon.
• IL-38, Dixon to Geneva.
• IL-31, Geneva to Aurora.
• US-30, Aurora to the Indiana Line.

Several towns have posted Lincoln Highway markers along the road, including some hand painted replicas of the original pole markers. Rochelle has pole banners, and many towns still call the road Lincoln Highway. The Lincoln Highway Association has a ton of information on this route.

SBI Route 31 was Quincy to Canton via

• US-24 Quincy to Beardstown,
• IL-100, Beardstown to near Havana,
• IL-78, Havana to Canton.
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• It was removed from these routes by 1935.
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• IL-31 was applied in 1937 to a road from Oswego to Richmond replacing:
• IL-22, Crystal Lake to Aurora (part of the "22 Loop"
• US-12, Crystal Lake to Richmond,
• US-30, Geneva to Aurora,
• US-32, Small portion at Aurora,
• US-34, Small portion at Aurora (Was US-32),
• US-330, Geneva to Aurora, was US-30,
• US-430, Richmond to Geneva.
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• There have been no changes since 1937.

IL-31 runs thru McHenry, Kane and Kendall Counties.

SBI Route 33 was Effingham to Gordon (Near Robinson).

• 1937 IL-33 was extended east to Palestine on the former IL-163.
• 1941 IL-33 was extended west to Beecher City.
• 1948 IL-33 was extended south from Palestine to US-50, on the IL side of the Wabash River, across from Vincennes IN.

In the 1960's it was extended slightly west on a stretch of former US-50, after US-50 was upgraded to a freeway.

SBI Route 37 was Mt. Vernon to Marion. In the mid 1930's IL-37 replaced IL-147 from Marion to Cairo, and IL-142 Mt. Vernon to Effingham, making IL-37 Effingham to Cairo. The first few miles out of Effingham were co-located with US-45, and this was dropped after the completion of I-57 in the early 1970's. In 1999 IL-37 was extended south a few miles on the old route of US-51 when US-51 was relocated to I-57 south of Dongola. I-57 parallels IL-37 most of the way to Cairo.

SBI Route 38 was Kampsville to Jerseyville over the current IL-100 (Kampsville to Nutwood) and IL-16 (Hardin to Jerseyville).

• In 1937 IL-38 north of Hardin was changed to IL-100 as an extension of that route.
• In 1937 IL-38 extended east to Mt. Olive replacing IL-110.
• In 1942 IL-38 was changed to IL-16 (west of Royal Lakes), IL-112 (Now IL-159) (Royal Lakes to IL-138) and IL-138 (IL-159 to Benld).
• From 1942 to 1971 IL-38 was not used.

In 1972 IL-38 replaced Alternate-US-30 from Dixon to Bellwood. The rest of Alt-US-30 was eliminated.

I-39 runs from I-55 near Bloomington to Wausau WI. The section from Rockford IL to Portage WI is just now being posted after not being so for several years. This section had always officially been I-39 (at least since I-39 was posted in WI several years ago) but not posted until recently. This had been considered for I-43, as the current I-43 ends just a few miles north of the IL line.

This route was an upgrade to US-51. In IL, US-51 has been moved to the Interstate, and most of the old road was changed to IL-251. In WI, US-51 is a separate road from the state line to Portage (As I-39 was routed over the existing I-90/I-94). North of Portage the road was upgraded in place and US-51 remained on the new road, although there are older alignments scattered about.

A future idea is to extend I-39 south. This would not be very difficult, since US-51 is already a 4 lane divided highway from the Bloomington area to Decatur. There has been speculation of extending I-39 to Decatur, running it around the East side of town to finish the loop, then going to either Vandalia or Effingham. If they go to Vandalia, then a logical extension of this would be to I-57 at Salem. This would allow traffic from the South to head north without heading towards Chicago. IDOT has no current plan to extend I-39 south of Bloomington at this time though.

Steve Sarver of Kirkland IL writes about I-39 (2001):

Portion from U.S. 20 near Rockford to IL-5 near Rochelle was opened in 1984. It was opened from IL-5 to I-80 in the fall of 1986. In December 1987, the section from I-80 south, across the Illinois River, was opened and its southern terminus was IL-251 (old U.S. 51). It was not open from IL-251 to IL-71. At one mile in length, the bridge is the longest in Illinois. It is named the Abraham Lincoln Memorial Bridge.
Meanwhile, construction began in late 1988 on the interchange with I-55 in Bloomington. During the summer of 1990, I-55 was reconstructed around Normal to handle an additional lane of traffic. The existing interchange of U.S. 51 and I-55 was closed completely and then reconstructed with its present configuration. Bridge work continued for the overpasses between Normal and Oglesby during the summer of 1990. The section from Oglesby to Normal contains a unique style of overpass construction that allowed for the elimination of the center pier.
During the summer and fall of 1991, segments of the new highway were opened south to IL-18. In 1992, more segments of the road were opened to traffic; the final segment was in the fall of 1992, completing the entire freeway from Rockford to Bloomington. IL-251 extends on most of the old U.S. 51; some minor rerouting was necessary because the new four-lane highway was built on top of the two-lane road. It is interesting to note that IL-251 terminates just north of Normal, while a four-lane “Business U.S. 51” was constructed over the old U.S. 51 for several miles north of Normal. There is a gap of several miles between the two. It is not known why IL-251 and Business U.S. 51 were not connected in some manner.
Andy Field’s “Interstate 39” page contains an error wherein he states that I-39 was called the “Central Illinois Expressway.” This is incorrect; the Central Illinois Expressway is I-72 from Champaign to Quincy.
Regarding the possibility of a crosstown expressway through Rockford with a I-x39 designation, this is doubtful as officials will probably never agree on a route, nor be willing to demolish a corridor necessary to build a road, interchanges, etc. It is more likely that U.S. 20 will one day carry an Interstate label.
The interchange of I-39/U.S. 51 and U.S. 20 is an incomplete cloverleaf. The road was designed to continue north into the south side of Rockford, possibly to Charles Street, to accommodate industry in that area. However the idea was discontinued due to heavy opposition from area residents. However, the interchange ramps were shaped during the earth-moving process and are visible to the present day. (Similar “ghost ramps” can be found north of Decatur for a future interchange there.) The merge areas for Interstate 39 SB and the ramp from EB U.S. 20 onto Interstate 39 SB were restriped in early 2001 to avoid confusion with the ghost ramp.
It has been suggested that a bypass around the east side of Decatur be built. However this is unlikely as the “ghost ramps” (mentioned above) are on the northwest side of Decatur. Also, the western bypass around Decatur was extended about a mile in 1994 to merge directly into the SB U.S. 51 (instead of a forced cloverleaf exit).
In the mid-1980’s, U.S. 51 was widened and upgraded to a four-lane divided highway between Bloomington and Decatur, with bypasses around some smaller towns. There are no present plans for an upgrade to Interstate standards (i.e., interchanges instead of at-grade intersections).
In mid-1995, rest areas were opened on both sides of Interstate 39 between Rockford and LaSalle (I-80). Prior to this time, “phantom exits” were built to illustrate where the actual ramps would be. Also, before the rest areas opened, “Truck Pull-Off Areas” existed on both sides of the highway several miles north of the rest areas. These are now closed and have since been fenced off to prevent access.

SBI Route 40 was Sterling to Mt. Carroll.

In 1938 IL-88 replaced IL-40 as an extension of that route.

In 1995 IL-88 was changed to IL-40, and extended from Peoria to East Peoria over the new bridge between the two cities since IL-88 conflicted with I-88 after IL-5 was changed to I-88 in 1992.

Business US-40 was on the old route of US-40 from East St. Louis to Collinsville (Vandalia Ave and Collinsville Rd.). This route was US-40 until 1962, changed to Alternate US-40 in 1963, then Business US-40 in 1964. Business US-40 was removed in 1974 as part of the Great Purge.

The National Road

The National Road was the first Federal Highway. In Illinois it followed the current route of US-40 east from Vandalia into Indiana. At Vandalia there is a monument near the Capitol (Vandalia was the state Capitol at the time).

To stay on the original National Road sections, take the blacktop from Casey thru Martinsville, and the one thru Marshall.

Route overview and markers