The huge boulder balanced on five smaller rocks near the town of North Salem, New York, is widely thought to have been carried to the area on moving glacial ice during the last ice age and deposited, by chance, on the supporting stones as the ice retreated.
Such a geological feature is called a glacial erratic and widely observed around the world, typically identified as such due to the rock being different in size and type to stone native to the area.
The Balanced Rock at North Salem is a type of pink granite not normally found in the immediate local area, but is seen further north in the Hudson Highlands. This suggests that the rock originated from outside the area, and given an estimated weight of over 60 tons, transport on ice flows would seem to be the most plausible explanation.