Marquette & Joliet, as imagined in 1921 by Frank Zeitler ("Marquette and Joliet Exploring the Upper Mississippi")
the first European explorers to reach Wisconsin were interpreters acting on behalf of Samuel de Champlain (q.v.). The first was probably interpreter Etienne Brule (q.v.), who in 1622 or 1623 traveled around Lake Superior at Champlain's request.
Because no account of his trip was written down until after Brule's death, Jean Nicolet (q.v.), who met with the Ho-Chunk at Red Banks (just north of the modern Univ. of Wisconsin-Green Bay campus) and whose trip was quickly chronicled, is usually called the first European explorer to reach Wisconsin. Other important early explorers who left eyewitness accounts (and who are described individually in the Dictionary of Wisconsin History) were Pierre Esprit Radisson and Medard Chouart, Sieur des Groseilliers, who visited in 1654-56 and 1659-1660; Jesuit missionaries Fr. Rene Menard (1661) and Jean Claude Allouez (1665-1670); traders Nicolas Perrot (1665-1670) and Daniel Greysolon, Sieur Duluth (1678-1680); Fr. Jacques Marquette, who crossed the state in 1673 with Louis Joliet en route to the Mississippi; and Recollect Fr. Louis Hennepin (1679-1680). Encouraging most of these men was Robert Rene Cavelier, sieur de LaSalle, who skirted the Lake Michigan shore of Wisconsin between 1679 and 1682.
Among other important European and American explorers to visit Wisconsin were Jonathan Carver (1710-1780), Zebulon Pike (1779-1813), and Lewis Cass (1782-1866).
View more information elsewhere at wisconsinhistory.org.