It is due east of Ennis Lake and its prominence and isolation makes it easy to distinguish from Ennis in the Madison River valley.

Jack and Cedar creeks are tributaries of the Madison River with headwaters on the eastern and western face of Fan Mountain.

The mountain straddles the northern boundary of the Spanish Peaks parcel of the Lee Metcalf Wilderness area.

Fan Mountain is a laccolith, a volcanic landform that is formed when magma pushes to the surface but does not flow out.

It is similar to the nearby Lone Mountain, another laccolith that was formed the same way.