Fiftymile Canyon lies between Davis Gulch and Willow Creek on the west shore of the Escalante Arm. The Hole-in-the-Rock Road crosses the head of the canyon about 50 miles from Escalante, Utah. Before the filling of Lake Powell, Gregory Natural Bridge spanned the canyon near its mouth. When the lake covered the bridge, the name was transferred downlake to the island butte at the mouth of Last Chance Bay. Herbert E. Gregory was a geologist who did extensive work in southern Utah and northern Arizona. Hikers can follow the canyon beyond Lake Powell all the way to the Hole-in-the-Rock Road.
