Wisconsin Highway 78

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State Trunk Highway 78

WIS 78 highlighted in red
Route information
Maintained by WisDOT
Length92.83 mi[1] (149.40 km)
Major junctions
South end IL 78 in Gratiot
Major intersections
North end I-39 / I-90 / I-94 in Portage
CountryUnited States
CountiesLafayette, Iowa, Green, Dane, Sauk, Columbia
Highway system
WIS 77 WIS 79

State Trunk Highway 78 (often called Highway 78, STH-78 or WIS 78) is a state highway in the U.S. state of Wisconsin. It runs north–south in south central Wisconsin from Portage to the Illinois border near Gratiot.


In the 1920s, Highway 78 was originally located on the Door County Peninsula on what is now Highway 57.

In 1963, the segment of STH-78 from the new I-90/I-94 freeway interchange south of Portage northerly to Highway 33 was improved to a four-lane divided facility. A year later, this four-lane divided highway (and the STH-78 designation with it) was extended northerly across the Wisconsin River then bypassing Portage to the west before merging into the existing two-lane route of US 51 north of the city. The entire four-lane divided portion of STH-78 from I-90/I-94 northerly to US-51 was shown as a full freeway with interchange beginning with the 1966 official state highway map, so it can be assumed the conversion to freeway occurred about this time (c.1965). In more recent decades, the short segment of STH-78 freeway was the only portion of the route from I-90/I-94 at Portage northerly past Wausau that was not signed as part of US-51, although signs along the route did indicate "TO US-51." Then in 1996, US-51 from Rothschild (south of Wausau) southerly to Portage was concurrently designated as Interstate 39 and to connect this new Interstate route with nearby I-90/I-94, the entire STH-78 freeway from US-51 north of Portage to I-90/I-94 was redesignated as part of I-39, with STH-78 losing approximately eight miles of length in the process.

Major intersections

LafayetteTown of Gratiot0.00.0
IL 78 south – Warren
Continuation into Illinois
WIS 11 west – Shullsburg
Western end of WIS 11 concurrency
WIS 11 east – Monroe
Eastern end of WIS 11 concurrency
WIS 81 west – Darlington
Western end of WIS 81 concurrency
WIS 81 east – Monroe
Eastern end of WIS 81 concurrency
IowaNo major intersections
GreenTown of York32.552.3
WIS 39 west – Mineral Point
Western end of WIS 39 concurrency
WIS 39 east – New Glarus
Eastern end of WIS 39 concurrency
DaneMount Horeb45.773.5 US 18 / US 151 – Madison, Dodgeville

Bus. US 18 east / Bus. US 151 east
US 151 exit 65; southern end of Business US 18 / Business US 151 concurrency

Bus. US 18 east / Bus. US 151 north / CTH-ID (Springdale Street) / WIS 92 south (8th Street)
Roundabout; northern end of Business US 18 / Business US 151 concurrency
Black Earth57.692.7
US 14 east – Madison
Southern end of US 14 concurrency

US 14 west / WIS 19 north – Spring Green
Northern end of US 14 concurrency; southern end of WIS 19 concurrency
Town of Mazomanie61.398.7
WIS 19 east – Waunakee
Northern end of WIS 19 concurrency
Town of Roxbury67.8109.1
US 12 east – Madison
Eastern end of US 12 concurrency
SaukSauk City68.4110.1

US 12 west / WIS 60 west (Phillips Boulevard)
Western end of US 12 concurrency; southern end of WIS 60 concurrency
Prairie du Sac70.0112.7
WIS 60 east (Prairie Street)
Northern end of WIS 60 concurrency
Town of Merrimac77.3124.4
WIS 113 north – Baraboo
Western end of WIS 113 concurrency
WIS 113 south – Merrimac Ferry
Eastern end of WIS 113 concurrency
ColumbiaTown of Caledonia92.83149.40
I-39 south / I-90 / I-94 – Wisconsin Dells, Madison

I-39 north – Portage
Roadway continues as northbound I-39
1.000 mi = 1.609 km; 1.000 km = 0.621 mi


  1. ^ Bessert, Chris. "Wisconsin Highways: Highways 70-79 (Highway 78)". Wisconsin Highways. Retrieved 2007-03-20.

External links