Interstate 39 (I-39): Illinois and Wisconsin Route, Miles and Crash Data

How long is I-39?

The FHWA Route Log gives I-39 322.08 miles as of January 2026: 140.04 in Illinois and 182.04 in Wisconsin. On this route the Route Log books shared pavement to I-39 rather than to I-90 or I-94. I-90's Illinois row notes 16.62 miles on I-39, the stretch from Cherry Valley to the Wisconsin line, and I-39's Wisconsin row also holds the miles it shares with I-90 and I-94 up to Portage. So the two rows add up to a full trip from Normal to the Wausau area.

Wikipedia lists 306.14 miles, the same total that Interstate Guide's two state figures add up to. Interstate Guide's Illinois figure, 123.42 miles, stops about where I-90 joins at Cherry Valley, which leaves out the 16.62 shared miles in that state. Its Wisconsin figure, 182.72 miles, is within a mile of the Route Log's. The crash rates on this page use the full 140.04 and 182.04 miles, shared stretches included.

Where I-39 starts and ends

I-39 begins at I-55 exit 164, just north of Bloomington-Normal, where US 51 joins it for the trip north. The northern end is the junction with WIS 29 and US 51 near Rothschild and Rib Mountain, about six miles south of Wausau. US 51 keeps going north to Merrill as a separate highway.

Heading north, the freeway crosses the Illinois River into LaSalle, passes between LaSalle and Peru, and reaches Rochelle and Rockford. In Wisconsin it goes through Beloit, skirts Janesville to the east, and runs past Madison and Portage before bypassing Stevens Point to the east and north. It crosses the Wisconsin River three times: before the Wisconsin Dells exit, at Portage, and again near Rothschild.

Interstate junctions along I-39

The list starts at I-55 in Normal and runs north. I-80 crosses near LaSalle and Peru, and I-88, a tollway, crosses at Rochelle. I-90 shows up twice. It joins I-39 at Cherry Valley near Rockford, and I-39 uses I-90's exit numbers from there to Portage. I-43 starts at the shared road in Beloit and heads for Milwaukee. I-94 comes in at the Badger Interchange in Madison, and the three routes run together for about 29 miles, which Interstate Guide calls the longest three-way overlap on the Interstate system. The second I-90 entry is the split near Portage, where I-90 and I-94 turn west toward Wisconsin Dells and I-39 continues north alone.

Fatal crashes on I-39

From 2020 to 2024, 59 people died in 50 fatal crashes on I-39, about 12 a year. Deaths went from 9 in 2020 to 15 in both 2021 and 2022, then fell back to 10 in each of the last two years. That works out to 3.7 deaths per 100 route miles a year, well under the Interstate average of 9.5. Among the 56 Interstates with enough mileage for a rate, I-39 ranks 52nd counting down from the highest.

Wisconsin had 43 of the deaths and a rate of 4.7. Illinois had 16 and a rate of 2.3. The counties with the most deaths are all on the Wisconsin side except one: Dane County, which holds Madison, had 15, and Columbia County, which holds Portage, had 11. Those two counties take in the stretch where I-39 runs with I-90 and I-94. Rock County and Marathon County, home to Beloit and Wausau, had 5 each, and Winnebago County in Illinois, around Rockford, had 4. The count takes the route from the road name on each FARS crash record, so some deaths on the pavement I-39 shares with I-90 and I-94 may be filed under those routes, while the rate counts all of the shared miles as I-39's. The true rate may be somewhat higher.

Counties with the most I-39 crash deaths

Bridges on I-39

The 2025 National Bridge Inventory counts 284 bridges carrying the I-39 main line: 166 in Wisconsin and 118 in Illinois. Only 3 rate Poor, about 1 percent, and all three are in Illinois. Another 109 rate Good and 172 Fair. Half were built in 1987 or later.

The Abraham Lincoln Memorial Bridge carries I-39 over the Illinois River from just north of Oglesby to LaSalle. Wikipedia puts it at 1.3 miles and calls it the longest bridge in Illinois. It opened in December 1987 with the section from I-80 south to IL 251.

Tolls on I-39

I-39's own road is free in both states. The one toll facility on its path in FHWA's January 2023 inventory is the Jane Addams Memorial Tollway, which is I-90. I-39 joins it at Cherry Valley and stays on it to the Wisconsin line, and the Illinois Tollway charges on that shared stretch, with an open-road plaza between Rockton and South Beloit. A trip the length of I-39 pays tolls only there. FHWA lists the tollway at 78.8 miles because it measures the whole road toward Chicago, far more than the 16.62 miles I-39 uses. Wisconsin has no tolls on I-39.

How I-39 was built and numbered

The first piece of I-39, from US 20 at Rockford south to IL 5 at Rochelle, opened in 1984. That December AASHTO turned down the Illinois application and suggested a three-digit spur number instead, then approved I-39 on reconsideration on January 3, 1985. The extension south to I-55 was approved on June 10, 1986, and the Illinois freeway was finished in 1992.

AASHTO approved the northern extension from Rockford to Wausau on October 22, 1993. North of Portage the number went onto the US 51 freeway; Wikipedia notes that US 51 was known as "Killer 51" before the freeway was built. Signs went up from Portage to Rib Mountain in 1996, and the stretch on I-90 and I-94 was signed in late 1998. In Illinois, the road from I-88 to the state line was named the E.J. "Zeke" Giorgi Highway on April 17, 2003.

Several large projects have rebuilt parts of the route since 2004. The Cherry Valley interchange with I-90 was rebuilt between 2008 and November 2010. From 2015 to 2021, WisDOT rebuilt 45 miles of 1960s freeway from the Illinois line to US 12/18 in Madison, widening it to six lanes, eight between WIS 11 and WIS 26, and reconfiguring 11 interchanges. Near Wausau, a $291 million project rebuilt about seven miles of US 51 and WIS 29 as a six-lane freeway between 2004 and 2010. An extension north to Merrill has come up, but WisDOT said in 2002 it had no plans to request one.

I-39 traffic and road conditions

Crashes, work-zone lane closures and snow on the road can change an I-39 trip within the hour. Illinois and Wisconsin each run a free traveler site with current incidents and conditions; pick the one for the state you are driving in.

I-39 questions