Narrow Dirt Road to Whipple Observatory, by Penland, Dane A, 1984, Smithsonian Archives - History Div, A winding, single-lane, dirt road 18 miles long connects the Smithsonian Astrophysical Observatory's Whipple Observatory atop Mount Hopkins in Arizona with the outside world. In 1984, a 1.5-mile section of the road at the very top, between the 8,550-foot summit and the 7,600-foot ridge was paved..