Prior to its designation as an Interstate Highway, the route was known as Illinois Route 5, and before that, Illinois 190.
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, NMSL was amended in 1987 to permit 65-mph (105 km/h) speed limits on rural stretches of Interstate highways only. In spite of the fact that IL 5 was fully up to Interstate standards, it still had to carry a 55 mph (88 km/h) limit because of this wording in NMSL. The Illinois Department of Transportation (IDOT) and Illinois State Toll Highway Authority (ISTHA) petitioned the American Association of State Highway and Transportation Officials (AASHTO) to re-designate IL 5 as an Interstate, and in 1988, AASHTO approved the request and assigned the Interstate 88 numbering to the highway. NMSL would be completely repealed only five years later in 1995, but the I-88 shields remain up to this day.
In honor of the 40th U.S. president, Ronald Reagan, IDOT renamed the freeway portion "Ronald Reagan Memorial Freeway" upon his death in 2004. Reagan was a native of nearby Dixon, Illinois. Similarly, ISTHA renamed the toll portion "Ronald Reagan Memorial Tollway." The tollway portion of I-88 was previously known as the "East West Tollway".
There is no direct off-ramp access to U.S. Route 52, Illinois Route 23, Illinois Route 25, and Illinois Route 83 (northbound). In addition, I-88 merges with Illinois Route 56 for a short distance. During the merge, Illinois 56 is the only tolled state route in Illinois.
As of 2007, I-88 has no spur routes. None are planned for the near future.
In 2005, ISTHA initiated a reconstruction and widening project for most of I-88 between Sugar Grove and York Road, a distance of 25 miles (40 km). On January 5, 2006 a fourth lane opened between Illinois 59 (mile 123.5) and Washington Street (mile 126.5), about 3 miles (5 km). In total, 5.7 miles (9.2 km) of roadway will be reconstructed, with construction continuing through 2008 from Washington Street to Finley Road(mile 131). Three lanes of traffic were reconstructed with continuously-reinforced concrete, and a fourth outside travel lane was added as a part of the project.
A fourth lane is to be added between Finley Road and Illinois 83 (mile 137) from December 2007 to the end of 2009. The portion of I-88 from IL 83 (mile 137) to York Road (mile 139) is to be widened and reconstructed in 2008ĘC2009.
On the western portion of the work zone, I-88 is to be widened to three lanes between Orchard Road (mile 115) and the Aurora Toll Plaza (mile 117.5), a distance of 3.4 miles (5.5 km). Included in the project is construction of a new bridge over the Fox River, reconstruction of the interchange with Illinois Route 31, and removal of a Burlington Northern Santa Fe bridge just west of IL 31. The work is to take place between summer 2007 and the end of 2009.
Binghamton to Oneonta
I-88 begins at an interchange with Interstate 81 just north of downtown Binghamton on the banks of the Chenango River. While both directions of I-81 are accessible from I-88 westbound, only one direction of I-81 (northbound) connects to I-88. The missing connection, I-81 south to I-88 east, is made via U.S. Route 11, NY 12 and NY 12A at I-81 exit 6. NY 12A then connects to I-88 at exit 2.
From I-81, I-88 heads east across the Chenango to Port Dickinson, where it merges with the limited-access NY 7 at exit 1. The two routes continue north, then east along the eastern bank of the Chenango River, where it meets NY 12A near Chenango Bridge. I-88 and NY 7 remain alongside the river to Port Crane, where the river begins to follow NY 369 (exit 3) northward. Outside of Port Crane, the expressway heads east to Sanitaria Springs. Here, NY 7 leaves the expressway at exit 4 and begins to parallel I-88, as it does for the remainder of I-88's routing.
I-88 continues east to Harpursville, interchanging with NY 79 (exit 6) near the center of the community. Shortly after meeting NY 79, I-88 reenters a river valley, this time that of the Susquehanna River. I-88 heads to the northeast, following the river and NY 7 to Sidney, where it meets NY 8, the primary north-south road through the village, at exit 9. From Sidney, I-88 progresses northeast through southern Otsego County, passing Unadilla before entering Oneonta. Within the city, I-88 interchanges with NY 205 ahead of an exit with NY 28. NY 28 joins the expressway, following I-88 out of the city.
Oneonta to Schenectady
Northeast of Oneonta, NY 28 leaves I-88 at exit 17 to follow the Susquehanna River northward toward Cooperstown. I-88, however, remains on a northeasterly track through rural eastern Otsego County. Upon crossing into Schoharie County, I-88 begins to follow an easterly routing as it heads toward Cobleskill. While NY 7 enters the village, I-88 passes south of it, connecting to the village via two exits with NY 7. East of Cobleskill, I-88 interchanges with NY 145. Howe Caverns, a regionally popular attraction, is located a short distance north of the exit. I-88 continues onward, skirting the northern edge of Schoharie before passing into Schenectady County.
Shortly after entering Schenectady County, I-88 meets U.S. Route 20 east of Duanesburg. Past US 20, I-88 continues northeast, interchanging with NY 7 for one final time before ending at the New York State Thruway (Interstate 90) in western Schenectady.