The story of Arches begins roughly 65 million years ago. At that time, the area was a dry seabed spreading from horizon to horizon. If you stood in Devils Garden then, the striking red rock features we see today would have been buried thousands of feet below you, raw material as yet uncarved. Then the landscape slowly began to change.
First, geologic forces wrinkled and folded the buried sandstone, as if it were a giant rug and someone gathered two edges towards each other, making lumps across the middle called Anticlines. As the sandstone warped, fractures tore through it, establishing the patterns for rock sculptures of the future.
The entire region began to rise, climbing from sea level to thousands of feet in elevation. What goes up must come down, and the forces of erosion carved layer after layer of rock away. Once exposed, deeply buried sandstone layers rebounded and expanded, like a sponge expands after it's squeezed (though not quite so quickly). This created even more fractures, each one a pathway for water to seep into the rock and further break it down.