Known in Anishnaabemowin as “Chi-sin,” the Big Rock has been used as a visual aid to water navigation since 1615. Through the centuries, it has been used as a gauge to determine the rise and fall of water levels in Lake Michigan. Michel de Lotbiniere described the rock in a letter sent back to France in 1749 as being at times, high and dry, and at other times, completely submerged. He concluded that the water in the Straits of Mackinac rose and fell by as much as 8 feet.
This large rock is approximately 33.8 feet in horizontal circumference, 9 feet high and 37 feet in vertical circumference. An estimated weight puts it around 54 tons.