The French explorers that discovered Illinois were Jacques Marquette and Louis Jolliet. They were the first Europeans to explore the Mississippi River and the Great Lakes region. They set out from Quebec in 1673 and traveled down the St. Lawrence River and into Lake Ontario. They then followed the Niagara River to Lake Erie and eventually to the Mississippi River. They explored the river as far south as the mouth of the Arkansas River before turning back. Their journey took them through present-day Illinois and several other states.