Interstate 39

Interstate 39 marker
Interstate 39
Map
I-39 highlighted in red
Route information
Maintained by IDOT, ISTHA and WisDOT
Length306.14 mi[1] (492.68 km)
Existed1986–present
NHSEntire route
Major junctions
South end I-55 / US 51 in Normal, IL
Major intersections
North end US 51 / WIS 29 near Rothschild, WI
Location
CountryUnited States
StatesIllinois, Wisconsin
CountiesIL: McLean, Woodford, Marshall, LaSalle, Lee, Ogle, Winnebago
WI: Rock, Dane, Columbia, Marquette, Waushara, Portage, Marathon
Highway system
IL 38IL US 40
WIS 38WI WIS 39

Interstate 39 (I-39) is a highway in the Midwestern United States. I-39 runs from Normal, Illinois, at I-55 to State Trunk Highway 29 (WIS 29) in the town of Rib Mountain, Wisconsin, which is approximately six miles (9.7 km) south of Wausau.[2] I-39 was designed to replace U.S. Route 51 (US 51), which, in the early 1980s, was one of the busiest two-lane highways in the United States.[citation needed] I-39 was built in the 1980s and 1990s.

In Illinois, the route has a total length of 140.82 miles (226.63 km).[3] In Wisconsin, I-39 has a distance of 182 miles (293 km). From Rockford, Illinois, to Portage, Wisconsin, I-39 runs concurrently with I-90. In Wisconsin, I-94 joins the pair in Madison until Portage. At 29 miles (47 km) in length, this concurrency of three Interstates is the longest in the country. From Portage northward, US 51 is cosigned with the Interstate and has exit numbers based on its mileage.

  1. ^ Starks, Edward (January 27, 2022). "Table 1: Main Routes of the Dwight D. Eisenhower National System of Interstate and Defense Highways". FHWA Route Log and Finder List. Federal Highway Administration. Retrieved December 6, 2023.
  2. ^ "Overview Map of I-39" (Map). Google Maps. Retrieved February 15, 2008.
  3. ^ Illinois Technology Transfer Center (2006). "T2 GIS Data". Illinois Department of Transportation. Retrieved November 8, 2007.