Interstate 41

Interstate 41 (I-41) is a 175.00 mi north–south Interstate Highway connecting the interchange of I-94 and U.S. Route 41 (US 41), located 2.50 mi south of the Wisconsin–Illinois border at the end of the Tri-State Tollway in metropolitan Chicago, to an interchange with I-43 in metropolitan Green Bay, Wisconsin. The designation travels concurrently with US 41 for its entire length, as well as portions of I-894, US 45, I-43, and sections of I-94 in Wisconsin and Illinois. The route was officially added to the Interstate Highway System on April 7, 2015, and connects Milwaukee and Green Bay with the Fox Cities.

Route description
I-41 begins at the I-94/US 41 interchange in Russell, Illinois, located 2.50 mi south of the Wisconsin–Illinois border at the end of the Tri-State Tollway. The highway continues north concurrently with I-94 as part of the North-South Freeway to the Mitchell Interchange in Milwaukee, turns west to run concurrently with I-894 and I-43 as the Airport Freeway to the Hale Interchange (forming a brief wrong-way concurrency with I-43), and turns north to run concurrently as the Zoo Freeway with I-894 and US 45 to the Zoo Interchange, with the US 45 concurrency continuing until the I-41/US 41/US 45 split near Richfield. The Interstate roughly parallels I-43, which runs north–south along Lake Michigan from Milwaukee to Green Bay. I-41 runs through the Fox Valley (including the cities of Fond du Lac, Oshkosh, and Appleton, along with the Fox Cities). At Appleton, I-41 intersects US 10 and State Trunk Highway 441 (WIS 441), the latter of which is a freeway that forms a beltway around Appleton by running around the south and east side of the city and back to I-41. Further north, I-41 intersects WIS 172 on the south side of Green Bay, before running along the city's west side to its end at the I-43 interchange. The Interstate is 175.00 mi long and located almost entirely within the state of Wisconsin and is completely concurrent with a slightly adjusted alignment of US 41 to its termination in Green Bay.

History
The freeway portion of US 41 and US 45 from Milwaukee through the Fox Valley to Green Bay was proposed and designated as an Interstate Highway as part of the 2005 highway funding bill (Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users).

In the initial language of the bill, the route was designated Interstate 41, which correlates with the U.S. Highway it parallels and also complies with the Interstate naming guidelines through the American Association of State Highway and Transportation Officials (AASHTO). The final bill omitted the I-41 designation. In 2009, Green Bay officials began a campaign to have US 41 designated as a northern extension of I-55 from its current termination in Chicago, with the alternative being designated as a spur of I-43. At the spring meeting of the Special Committee on U.S. Route Numbers of AASHTO on May 18, 2012, the I-55 designation was discussed by the committee. Coordination would have been required with the Federal Highway Administration (FHWA) and the Illinois Department of Transportation (IDOT) on the I-55 designation.

However, IDOT officials were not interested in signing an extension of I-55 from its Chicago terminus to the state line. Therefore, the Wisconsin Department of Transportation (WisDOT) decided to seek a different designation not requiring the cooperation of their Illinois counterparts. Four designations were proposed by WisDOT and put up for public review: two new primary designations (I-41 and I-47) and two auxiliary designations (I-594 and I-643). At the end of October 2012, WisDOT submitted I-41 to AASHTO for consideration at their fall Special Committee meeting, where it was conditionally approved on November 16, 2012, pending FHWA concurrence. Official approval of I-41 then hinged on weight limit exceptions being approved for the route, which initially passed the United States House of Representatives as H.R. 4745 and awaited a United States Senate vote as S. 2438, but there were later passed in a different bill (H.R. 83) on December 16, 2014. On April 9, 2015, Wisconsin Governor Scott Walker announced that the FHWA had approved I-41 as part of the Interstate Highway System. According to WisDOT, the approval came two days earlier.

WisDOT replaced or modified 3,500 signs before and near September 2015 after coordination with IDOT and the FHWA (signs erected in 2014 and into 2015 before approval of the designation had the I-41 shield obscured until approval). Over the next 5–10 years, shoulders are slated to be rebuilt as older parts of the highway are rebuilt. The redesignation to Interstate status also makes the route subject to the Highway Beautification Act, meaning current advertising billboards along the Milwaukee-to-Green Bay portion of the road can no longer be upgraded or enlarged nor can new signs be added.

Future
Beginning in early 2024, WisDOT plans to start several projects to improve I-41 in the Appleton area between Neenah and De Pere. The projects will include widening the Interstate from two to three lanes in each direction on a 23 mi stretch between Appleton and De Pere, upgrading interchanges, reconstructing bridges, and repaving sections of the freeway, along with the new South Bridge Connector project adding a new Fox River span south of De Pere with an I-41 interchange. These projects are expected to be completed by 2026.