Road 400 (Cottonwood Canyon Road) connects the Page, Arizona area near Glen Canyon Dam via U.S. Route 89 with Cannonville, Utah near the entrance to Bryce Canyon National Park and traverses portions of Grand Staircase-Escalante National Monument. Road 400 is an alternative to US-89 for drivers wishing to avoid US-89's long western detour around the scenic National Monument. Instead, Road 400 offers a unique, little-known shortcut through the monument itself, rarely marked on large-scale planning maps.
Road 400 is a good quality dirt road (mostly a thin coating of sand and dust over smooth sandstone) that allows passage of ordinary vehicles during dry weather (confirm road conditions locally before use). Originally constructed as a maintenance road for power lines traversing the canyon, it is considered impassable in wet weather as several dry washes are crossed near each end of the road and portions may be inundated by fast stormwater runoff. In spring conditions such locations should be crossed with caution, even when low or dry, in order to avoid being caught in a flash flood.
Patient drivers of this road will be rewarded with a close look at spectacular geological features, which while not especially large are jagged, varied, and colorful. Owing to dusty conditions, fast driving is discouraged, so extra time should be allowed if this route is used. The only other unpaved road traversing the entire Grand Staircase is to the east and is only suitable for high clearance four wheel drive vehicles.
At the southern entrance of Road 400, a sign says "IMPASSIBLE WHEN WET / 8 MI. COTTONWOOD CANYON / 30 MI. GROSVENOR ARCH / 46 MI. CANNONVILLE."
As of mid-2006, Road 400 is a dirt road all the way from US-89 in the south past the Grosvenor Arch area, where eventually becoming paved some miles prior to Cannonville.
A good overview of the terrain in this region may be seen at the project relief map at the Glen Canyon Dam interpretive center, located on the North side of the Glen Canyon overlooking the downstream face of the dam, where the road crosses over the bridge.
The canyon may be located on satellite images by starting from Lake Powell. The large, eroded area to the northwest is the Grand Staircase. The canyon is identified by the relatively straight gouge at the western boundary of this area running slightly east of north, in the center of Kane County.