Negro Bill Canyon (Grand) was named for William Granstaff, a black rancher and prospector in the area around the late 1800s. It originates near Porcupine Rim, the twelve-mile-long steep slope along the western edge of Castle Valley. The canyon has a perpetual stream which runs about eleven miles to the west where it empties into the Colorado River. Negro Bill Canyon can be accessed from scenic highway 128 north of Moab. Morning Glory Arch is an alcove type arch with a 243' (74.07m) span. It is found in the second side canyon ca. 1.70 miles from the trail head, then about .30 miles off the main canyon.
G. William Wiersdorf
See: Natural Arch and Bridge Society, John W. Van Cott; Utah Place Names.