Grant County is the most southwestern county in the U.S. state of Wisconsin. As of the 2020 census, the population was 51,938. Its county seat is Lancaster and its largest city is Platteville. The county is named after the Grant River, in turn named after a fur trader who lived in the area when Wisconsin was a territory. Grant County comprises the Platteville Micropolitan Statistical Area. It is in the tri-state area of Wisconsin, Illinois, and Iowa, and is crossed by travelers commuting to Madison, Wisconsin, from a number of eastern Iowan cities, and by residents of northern Illinois traveling to the Twin Cities or La Crosse, Wisconsin.

U.S. Route 61 or U.S. Highway 61 (U.S. 61) is a major United States highway that extends 1,400 miles (2,300 km) between New Orleans, Louisiana and the city of Wyoming, Minnesota. The highway generally follows the course of the Mississippi River and is designated the Great River Road for much of its route. As of 2004, the highway's northern terminus in Wyoming, Minnesota, is at an intersection with Interstate 35 (I-35). Until 1991, the highway extended north on what is now Minnesota State Highway 61 through Duluth to the Canada–U.S. border near Grand Portage, then continued to Thunder Bay, Canada, as Ontario Highway 61. Its southern terminus in New Orleans is at an intersection with U.S. Route 90. The route was an important south–north connection in the days before the interstate highway system.