Marquette is a city in Clayton County, Iowa, United States. The population was 421 at the 2000 census. The city, which is located on the Mississippi River, is named after Jesuit missionary Jacques Marquette, who along with Louis Joliet discovered the Mississippi River just southeast of the city on June 17, 1673. Marquette is located directly across from Prairie du Chien, Wisconsin, and the two cities are connected by U.S. Highway 18, which crosses the river on the Marquette-Joliet Bridge. Effigy Mounds National Monument and the Yellow River State Forest are a few miles to the north. The city of McGregor, Iowa is located just to the south. Marquette itself was originally incorporated as North McGregor in 1874, and it served as a railroad terminus for its southern neighbor. Along with McGregor, the city became a major hub on the railroad, as grain from throughout Iowa and Minnesota was sent through the city en route to Lake Michigan.