Interstate 43

Interstate 43
I-43 highlighted in red
Route information
Maintained by WisDOT
Length	191.55 mi[1] (308.27 km)
Existed	1981[2]–present
Tourist routes	Lake Michigan Circle Tour
NHS	Entire route
Major junctions
South end	I-39 / I-90 in Beloit
Major intersections	US 14 in Darien US 12 in Elkhorn US 45 / WIS 100 in Greenfield I-41 / I-94 / I-894 / US 41 in Milwaukee WIS 23 in Sheboygan US 151 / WIS 42 in Manitowoc WIS 54 / WIS 57 in Green Bay
North end	I-41 / US 41 / US 141 in Howard
Location
Country	United States
State	Wisconsin
Counties	Rock, Walworth, Waukesha, Milwaukee, Ozaukee, Sheboygan, Manitowoc, Brown
Highway system
Interstate Highway System Main Auxiliary Suffixed Business Future Wisconsin State Trunk Highway System Interstate US State Scenic Rustic
← WIS 42 → WIS 43

Interstate 43 (I-43) is a 191.55-mile-long (308.27 km) Interstate Highway located entirely within the US state of Wisconsin, connecting I-39/I-90 in Beloit with Milwaukee and I-41, U.S. Highway 41 (US 41) and US 141 in Green Bay. State Trunk Highway 32 (WIS 32) runs concurrently with I-43 in two sections and I-94, I-894, US 10, US 41, US 45, and WIS 57 overlap I-43 once each. There are no auxiliary or business routes connected to I-43, though an alternate route to direct traffic during road closures is signed along local and state highways from Milwaukee County north into Brown County.

I-43 came about as a result of toll road proposals that included a Milwaukee to Superior corridor that included Hurley, Wausau, and Green Bay. Only the Milwaukee-to-Green Bay section was approved. The route was originally planned to follow an alignment about midway between US 41 and US 141 (the latter paralleled Lake Michigan at the time) along WIS 57. Controversy about this location and use of right-of-way led to the establishment of the current alignment, which follows much of what was the 1950s-era realignment of US 141 from Milwaukee to Sheboygan, and a new alignment from Sheboygan to Green Bay. This section was completed in 1981.

The Beloit-to-Milwaukee segment was developed after two separate proposals for Interstates, one of them between Milwaukee and Beloit and the other between Milwaukee and Janesville. The Milwaukee–Beloit route was chosen, completed in 1976 as WIS 15 and renumbered as I-43 in 1988. To connect the two segments, I-43 was signed concurrently with the east–west segment of I-894 and the north–south portion of I-94 in the greater Milwaukee metropolitan area from I-894 to the Marquette Interchange, which was completely reconstructed with work being completed in 2008.