The Bowlus SP-1 Paperwing was an American high-wing cantilever monoplane, single-seat, glider that was designed in 1928 and completed by William Hawley Bowlus on January 1, 1929. The SP-1 was Bowlus' sixteenth glider, and was test flown at Lindbergh Field in San Diego in January, 1929. Later tests were also made from hillsides near Bonita, California in April, 1929. SP-1 received identification mark "493" from the United States Department of Commerce and was one of the first licensed gliders in the United States. Many refer to the Bowlus SP-1 as the first sailplane of U.S. design and construction.