 MacGregor planned the new city as a six block development, and it was quickly populated, being incorporated as McGregor in 1857.In that same year, the Milwaukee & Mississippi Railroad finished building a railroad track from Milwaukee, Wisconsin to Prairie du Chien, Wisconsin, thus connecting Lake Michigan with the Mississippi River by rail.McGregor quickly became a major commercial center, and served as a hub where grain from Iowa and Minnesota could be transported across the Mississippi and sent on to Milwaukee via railroad.