Interstate 39

Interstate 39 is an Interstate Highway in the Midwestern United States that runs north–south through Illinois and Wisconsin, connecting Rockford, Peoria, and Wausau. Commissioned in the mid-1980s, it provides a higher-capacity corridor paralleling parts of U.S. Route 51 and linking with major east–west routes such as Interstate 90, Interstate 80, and Interstate 94. The route serves regional freight, commuter, and long-distance traffic and traverses a mix of urban, suburban, and rural landscapes including portions of the Rock River valley and the Wisconsin River basin.

Route description

Interstate 39 begins near Rockford at an interchange with Interstate 90 and proceeds southward through the Winnebago County corridor, intersecting US 20 and passing near Belvidere and Janesville metropolitan influences before meeting I-88 near DeKalb. Continuing as a freeway, it overlaps with Interstate 80 and Interstate 74 in the Bloomington–Normal area and provides access to Illinois State University. Farther north, the highway runs concurrent with U.S. Route 51 toward LaSalle County and Peru, crossing the Illinois River and serving industrial zones adjacent to Peoria. Crossing into Wisconsin, the roadway continues concurrent designations with US 51 through Rock County and Dane County, intersects Interstate 90 near Madison, and proceeds northward past Portage toward Stevens Point. The northern terminus lies near Rhinelander, tying into regional routes that serve the Northwoods and recreational destinations such as Lake Superior watershed access points.

History

The corridor that became the Interstate was influenced by earlier federal highway projects including U.S. Route 51 and state efforts in Illinois Department of Transportation planning and the Wisconsin Department of Transportation. Designation as an Interstate in 1984 followed coordination with the American Association of State Highway and Transportation Officials and approval processes involving the Federal Highway Administration. Construction phases paralleled economic shifts in the Rust Belt and agricultural regions, with major segments completed in the late 1980s and early 1990s. Key engineering milestones included river crossings over the Illinois River and upgrades near Peoria to accommodate freight traffic serving Caterpillar Inc. facilities and other industrial employers. Subsequent upgrades addressed safety concerns from winter weather common to the Great Lakes region and integrated with regional planning led by metropolitan planning organizations in Bloomington and Madison.

Exit list

The highway's exits provide connections to a range of federal and state routes. Major interchanges include connections with Interstate 90 near Rockford, Interstate 88 near DeKalb, the I‑80/I‑74 complex around Bloomington–Normal, and Interstate 94/U.S. Route 12 access points near Madison. Other significant exits serve US 20, US 30, US 6, and US 10, plus state highways such as Illinois Route 251 and Wisconsin Highway 13. Interchanges also provide access to regional airports including Chicago Rockford International Airport, Greater Peoria Regional Airport, and Central Wisconsin Airport, as well as educational institutions like Illinois State University, Bradley University, and University of Wisconsin–Stevens Point.

Services and traffic

Service plazas, truck stops, and rest areas along the route cater to freight carriers serving distribution centers for companies such as John Deere, Kraft Foods, and Amazon. Traffic volumes vary widely: urban segments near Rockford, Bloomington, and Madison experience peak commuter flows linked to employment centers including University of Illinois affiliates and regional hospitals, while rural stretches support seasonal recreational traffic heading toward Chain O'Lakes State Park and northern lakes near Rhinelander. Maintenance regimes are coordinated between state agencies to address snow removal influenced by lake-effect precipitation from the Great Lakes and commercial vehicle enforcement tied to Federal Motor Carrier Safety Administration regulations.

Future and proposed developments

Planned improvements include interchange reconstructions and capacity projects prioritized by the Illinois Department of Transportation and the Wisconsin Department of Transportation in statewide transportation improvement programs. Proposals under consideration involve auxiliary lanes near growing suburbs around Rockford and safety enhancements in the Portage corridor to support freight movement connecting to Interstate 94 and Interstate 90. Environmental and funding reviews engage stakeholders such as regional planning commissions and freight advisory councils, with potential federal grants from programs administered by the Federal Highway Administration influencing timelines. Longer-range concepts have examined limited-access upgrades and technology deployments tied to Intelligent Transportation Systems demonstrations and truck parking strategies coordinated with private operators.

Category:Interstate Highways in Illinois Category:Interstate Highways in Wisconsin