Hi!
The correct option would be Lead.
Michigan, Wisconsin and Minnesota were rich in natural sources, and prospective areas for miners to settle. Miners would move in search of gold, silver, copper and iron which were present in abundance in the mines of the aforementioned areas.
Gold was the cause of the mass movement to the far West in 1849 -the news of gold being discovered in California resulted in people selling their belongings and possessions to move to West, and resulted it in a fast settlement in the area, making it a state of the union in 1850.
Lead did not attract western settlers in the 1800's.
Hope this helps!