^Looking south down the northern beginning of Wisconsin 78 as the pavement of Interstate 39 continues beyond Interstates 90 and 94 near Portage, July 2025.

Wisconsin Highway 78 is a north-south highway in southern Wisconsin. If you want to be nitpicky, it takes more of a south-southwesterly course from its northern end in Portage. It begins on the pavement that Interstate 39 abandons for a triplicate concurrency along Interstates 90 and 94. From the point of beginning where this happens, Wisconsin Highway 78 heads southwesterly to flirt with the western banks of the Wisconsin River, passing through Merrimac and Prairie du Sac. At Sauk City, the twin city of Prairie du Sac, Highway 78 crosses the westward-turning Wisconsin River to continue south. It meets Wisconsin Highway 19 and US Route 14 in Mazomanie, then it meets US Route 18 and Wisconsin Highway 92 in Mount Horeb. South of here, Highway 78 wiggles its way through the hills, pushing toward the south-southwest. It meets Wisconsin Highway 81 in Argyle, and it meets Wisconsin Highway 11 in Gratiot. South of Gratiot, Wisconsin Highway 78 ends by meeting the Illinois state line. The highway continues with a matching number, as Illinois Route 78.

My photo of a route marker for Wisconsin Highway 78 shows a dual guide marker at the eastern entrance to the small village of Gratiot, Wisconsin. Highway 78 joins Wisconsin Highway 11 westward at a point just east of town; this signage reassures people that they are on the right path if they want to use Highway 11 west or Highway 78 south. This photo was taken in October 2016 during a day trip to points in southwestern Wisconsin.
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