Grand Tower Island is a river island in the Mississippi River in the midwestern United States, within the state of Missouri on its border with the state of Illinois.[1] Formed within recorded history by the movement of the river, it consists of a bulge-shaped piece of land between the river's primary channel and an oxbow lake. Land on the island is generally valuable for farming, especially when protected from flooding, while the lake has developed a reputation as a valuable sport-fishing location.