Minnesota State Highway 23 (MN 23) is a state highway that stretches from southwestern to northeastern Minnesota. At 343.723 miles (553.169 km) in length, it is the second longest state route in Minnesota, after MN 1.This route, signed east–west, runs roughly diagonally across Minnesota from southwest to northeast. It indirectly connects Duluth to Sioux Falls, South Dakota, and passes through the cities of St.