State Trunk Highway 100 (STH-100, commonly known as Highway 100 or WIS 100) is a road which encircles the outer edges of Milwaukee County, Wisconsin, United States.

Quick Facts State Trunk Highway 100, Route information ...

State Trunk Highway 100
WIS 100 highlighted in red
Route information
Maintained by WisDOT
Length	39.69 mi[1] (63.87 km)
Major junctions
South end	WIS 32 in Oak Creek
Major intersections	I-41 / I-94 / US 41 in Oak Creek US 45 / WIS 36 in Franklin I-43 / US 45 in Greenfield I-94 in West Allis US 18 in Wauwatosa US 45 in Wauwatosa US 45 in Milwaukee I-41 / US 41 / WIS 175 in Milwaukee I-41 / US 41 / US 45 in Menomonee Falls
North end	I-43 / WIS 32 in Bayside
Location
Country	United States
State	Wisconsin
Counties	Milwaukee, Waukesha
Highway system
Wisconsin State Trunk Highway System Interstate US State Scenic Rustic
← WIS 99 → WIS 101

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The road is designed as a bypass around the city of Milwaukee, but with residential and commercial development along WIS 100 on almost all portions of the road, this purpose has been negated, and it serves as one of the Milwaukee area's major commercial corridors. WIS 100 roughly parallels the freight railroad beltway around Milwaukee constructed in 1912 by the Chicago and North Western Transportation Company, approximately one mile inside the north, west and south county lines.

In Milwaukee's immediate western suburb Wauwatosa, WIS 100's north–south segment was once known as Lovers Lane; parts of the road still have this designation. In the vicinity of Mayfair Shopping Center, it is known as Mayfair Road; this corresponds to 108th street in Milwaukee's numbered roadways scheme.

The roadway served the Muirdale Tuberculosis Sanatorium and County Airfield and Limestone Quarry at what is now Currie Park. In the late 1950s, due to the combination of ready roadway and rail access, the area experienced an employment boom as several large cold storage warehouses and food-related truck terminals were constructed nearby. With the development of Mayfair in 1958 by malting scion Kurtis Froedtert, the name was changed to Mayfair Road.

One of the few vestiges of this earlier era is the roadway's popularity as a cruising strip for mainly young motorists showing off their vehicles. West Allis and Milwaukee eventually cooperated to attempt to outlaw cruising on the road as a violation of unlawful assembly statutes, which result in the fining of drivers and impoundment of their vehicles.^[2] Signs are posted along the road to remind motorists of the law, including in West Allis, where the threshold is the passing of a controlled point more than three times in a certain period.

Between 1920 and 1923, WIS 100 was designated via parts of modern-day WIS 138 and US 51.^[3][4] The entirety was replaced by a new alignment of WIS 10.^[5][6]

The current alignment of WIS 100 was initially a county-constructed concrete loop highway known as County Trunk Highway L.^[7] WIS 100 was then assigned in 1923 along part of the county highway as well as WIS 15 (now superseded by US 41) and WIS 74.^[5][6]

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