Augustus Roy Knabenshue was born July 15, 1876 in Lancaster, Ohio to Samuel S. and Salome Knabenshue. The family later moved to Toledo, Ohio where Roy's father became editor-in-chief of the Toledo Blade. It was there that Roy became interested in lighter-than-air flight after seeing a balloon ascension when he was only five years old. His interest continued to grow in the years that followed and in 1899 he bought a captive balloon and its equipment. The next season, he began to take short leaves of absence from his job at Central Union Telephone Company and was operating his balloon at fairs and carnivals, charging attendees for ascensions. To protect his day job and spare his socially prominent family embarrassment, Knabenshue used the name "Professor Don Carlos" at his balloon engagements. By 1900, Knabenshue had begun to fabricate additional spherical balloons himself, for use in free ascensions.
In October of 1904, Knabenshue took a new balloon to Saint Louis to enter it in contests associated with the First World's Fair, also known as the Louisiana Purchase Exposition. There he met Thomas S. Baldwin, who had brought his dirigible California Arrow to the event. The airship proved incapable of taking off with Baldwin at the helm and the slimmer Knabenshue was asked to substitute as pilot. Possessing no experience with dirigibles, Knabenshue accepted Baldwin's instructions and on October 25 became the first person to successfully pilot a dirigible in the United States.
Roy Knabenshue's name would be associated with the term "first" many times in the next few years. In 1905, Knabenshue built his own airship, the Toledo I, and flew it at its namesake city on Independence Day. It was the first streamlined dirigible in United States. A month later, Knabenshue made the first flight of an airship over Manhattan, taking off from Central Park and circling the Times Building. On December 17, 1908, he made the first successful night flight of a dirigible in the United States.
By 1909, Roy had teamed up with Lincoln Beachey to fly airships at various events. Beachey was to fly a Knabenshue dirigible a year later at the First International Aviation Meet held in the United States. Roy Knabenshue was instrumental in organizing that meet at Dominguez Field, Los Angeles, and raced his own airship during the events, setting several records.
His success attracted the attention of the Wright Brothers, who were considering entering the exhibition field. Knabenshue was hired to manage their exhibition team and did so beginning in 1910 and periodically for the next few years. Associated professionally at times with Glenn Martin, Walter Brookins and James V. Martin, by 1917 he had formed the Knabenshue Aircraft Corporation to produce dirigibles, kite balloons and parachutes. During the First World War, this company made captive observation balloons for use by the United States Navy.
In 1933, Knabenshue began work for the United States Department of the Interior's National Parks Service. His duties included surveying air routes and the management of an autogiro project.
After suffering a heart attack in 1949, Knabenshue retired. He passed away on March 6, 1960 at the age of 83 and was interred at the Portal of the Folded Wings, Valhalla Memorial Park, North Hollywood, California. He had held Balloon License Number 31, Dirigible License Number 4, built ten airships and numerous balloons, was a prominent member of the Early Birds and had earned a significant place in American aviation history.