During the Cretaceous period between 66 and 144 million years ago, a range of mountains known as the Sevier mountains rose in western Utah.  Over millions of years of erosion, streams brought down the mountains and spread their sediment over a broad fan to the east.  In some places the sediment reached 15,000 feet deep.  At greath depths, the pressure and heat were enough to fuse the river cobbles and mud into a rough conglomerate rock.

Millions of years later regional uplift created Utah's high plateau regions.  The San Pitch mountains lie along the western edge of one such plateu and are composed mostly of the uplifted Sevier conglomerate.  Here in Maple Canyon and Box Canyon in particular, the ancient river deposits are exposed and cut into slots, hoodoos, arches and amphitheaters.