On October 22, 1960, Yost lifted off from Bruning, Nebraska, on the first-ever free flight of a modern hot-air balloon. His balloon flew untethered for 1 hour and 35 minutes with the aid of heat generated by a propane burner. The balloon’s 40 ft (12 m)-diameter envelope was sewn from heat-resistant fabric specially selected by Yost for the purpose. In November 1960, Yost made a second flight with an improved balloon from the famed Stratobowl, near Rapid City, South Dakota.
Text from Wikipedia. https://en.wikipedia.org/wiki/Ed_Yost