When the Wright brothers were here, Big Kill Devil Hill was a massive sand dune. Thousands of times, the brothers trekked up this hill and three nearby dunes to conduct glider experiments. Climbing the hill was strenuous because deep, soft sand caused every step up the slope to slip part-way back down. The Wrights also carried their heavy gliders up the hill for each flight. Their tireless efforts paid off as they mastered their flying skills and refined their flight controls.