East of Rock Falls, the route is a part of the Illinois Tollway system.

In DeKalb, they meet Annie Glidden Road at a trumpet interchange, then cross over IL 23 without direct access, serve DeKalb Oasis, and meet Peace Road at a four-ramp parclo.

South of Nottingham Woods, they meet IL 47 at a five-ramp parclo with two ramps.

After that, I-88 and IL 110 then meet Midwest Road at a two-ramp incomplete parclo (no westbound on/offramp), then IL 83 at a three-ramp incomplete parclo, 22nd Street at a right-in/right-out (no eastbound on/offramp), another mainline toll plaza for westbound traffic, and I-294/IL 38.

[8] The reason for I-88's original designation and continued existence as an Interstate has to do with a technicality in the old National Maximum Speed Law (NMSL).

Originally passed in 1973, the NMSL was amended in 1987 to permit 65-mile-per-hour (105 km/h) speed limits on rural stretches of Interstate Highways only.

Even though IL 5 was fully up to Interstate Highway standards, it still had to carry a 55-mile-per-hour (89 km/h) limit because of this wording in NMSL.

[1] The NMSL would be completely repealed only eight years later in 1995, but the I-88 shields remain to this day, even though Chicago–Kansas City Expressway (IL 110) markers are being posted throughout the entire length of I-88, since it is now part of the Chicago to Kansas City Expressway project, bannered with special "CKC" logos.

The original routing extended from the I-294 interchange near Hillside to IL 47 near Sugar Grove.

IL 56 was overlapped on the East-West Tollway between North Aurora and Sugar Grove in 1965.

Once complete, the new routing of the combined tollway and freeway between I-80 near the Quad Cities and I-294 became designated as IL 5.

After the death of Illinois native and former President Ronald Reagan in 2004, ISTHA voted to rename the toll roadway "Ronald Reagan Memorial Tollway" in his memory, as it passes near his birthplace of Tampico and grazes the south outskirts of his boyhood hometown of Dixon.

From 2005 lasting through 2012, ISTHA reconstructed and widened much of the original portion of I-88, between York Road and IL 56.

[10] Between 2005 and 2009, I-88 was reconstructed and widened to four lanes in each direction between IL 59 and York Road, with work progressing gradually from west to east.