The story begins nearly 2.7 billion years ago with some of the oldest rocks found in any American national park . But the most dramatic chapters were written relatively recently in geological terms. The Teton Range is actually the youngest mountain range in the Rocky Mountain chain, less than 10 million years old, with its signature peaks still rising today while Jackson Hole valley continues to sink .

This striking landscape formed when two massive blocks of the earth's crust behaved like giant trapdoors swinging in opposite directions. The western block (the Teton Range) lifted along the Teton Fault, creating those spectacular eastern faces that soar over 7,000 feet above Jackson Hole. Meanwhile, the eastern block (Jackson Hole) dropped downward, tilting the valley floor toward the mountains . French trappers named these distinctive peaks "les trois tétons" (the three breasts), later shortened to Tetons .

The final sculpting came during the last Ice Age when glaciers carved the characteristic U-shaped canyons and left behind the chain of sparkling lakes at the base of the mountains. Even today, small glaciers persist near the highest peaks, though they continue to recede .